Chapter 1. Chapter 31: Immune System

1.1 Introduction

Interactive Study Guide
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Polaris Trail

Welcome to the Interactive Study Guide for Chapter 31: Immune System! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

The Forgotten Plague:

After nearly a century, scientists learn what made the 1918 influenza virus so deadly.

DRIVING QUESTIONS

  • What is the structure of a virus, and how do viruses cause disease?
  • What is innate immunity?
  • What is adaptive immunity, and how does vaccination rely on it?
  • What specific features of influenza virus allow it to cause worldwide outbreaks?

1.2 Driving Question 1:

Driving Question 1

What is the structure of a virus, and how do viruses cause disease?

Why should you care?

Viruses cause diseases ranging in severity from the common cold to Ebola. Some, like the common cold virus, cause disease symptoms shortly after infection. Others, like HIV, can remain dormant for long periods before beginning to affect the host. With many viruses, recovery happens relatively quickly as the immune system gets rid of the invaders. Others, like the herpesvirus that causes cold sores or the varicella virus that causes chicken pox in children and the painful condition known as shingles in adults, cause latent infections: the virus is never eliminated but goes through periods of dormancy and activity for reasons that are not clearly understood. Viral diseases are difficult to treat; understanding how viruses infect and replicate in their host cells can help you understand why.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Diagram a typical virus.
  2. Diagram and describe the general process of viral infection and replication.
  3. Explain how replicating viruses can kill host cells.

Infographic Focus

The Infographics most pertinent to the Driving Question are 31.1 and 31.2.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
dbhizUvf6ut1L1VJMWGALIfcQ/ZleC0cWNN9N7b0a71YtaLO Infectious agents, including certain viruses, bacteria, fungi, and parasites. Many pathogens trigger an immune response.
WApubn399yVCaRcjluIHKGWOqylC7lt0AHBrMXder56GbEaT An acellular infectious particle consisting of nucleic acid surrounded by a protein shell.
Ses3PwMYfuuj1WaABhSWyl9ZiDmyOdkuZ/qlznQpp8fFFXr/ A system of cells and tissues that acts to defend the body against foreign cells and infectious agents.
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Diagram a typical virus.

Question 1.1

cEEq9LNfuyqvmzYyxnS/AXSmVC/PmjZBZ0OnMl7A/4vA2L7+NG1TYgAfSeQKZ6WAwaOnLNFqPtRdoFb5tkcSK/FtCTcnk8f3

Diagram and describe the general process of viral infection and replication.

Question 1.2

AOoSIwcWb/tZo6mjoof3xe7B/uWTC6mVUjdokLRh+QTX8GmI7sUkTcXhv2NyqyEOMTR+H5pAMpq7md1FULMdqewAdtR2vPpqikmv4VxlEMQDAGz4uozSYyAXpFy9PZnXcIm91Vk1YIcroNXThWIquaipwrcc911YVki9xQR7NNuRCF8voD3V+pWii6oK0OYOB7vYWcDrSk2tX5gJkf6I4ZDhInCXotS2o4wBes4DJS6WFvmjdK0/BXV5ZZkkT5XN50HrrpbGNno=

Explain how replicating viruses can kill host cells.

Question 1.3

5fe81JlkeAs2I+uQZ4qdDWp1qE5r8tme3y5JqxbIWniBuXQeYfWVo97+IYkcE/AZZzWrLkqZ9tSsjYsc9qRMUIWPRdnRN2SxT4Ayiw4PAfABycJw87UN79OEiAMyNZRxhs3+alk0IdFMYerQSK+CTzyTnHo=
Replicating viruses can kill their host cells either directly by physical means or indirectly via the immune system. Some physically burst from the cell, causing cell death, and some hijack cellular machinery for so long that the cell eventually dies. A damaged or dying cell will be identified as such by the immune system, which will mount an attack on the tissue; this is not necessarily bad, but if the immune response is too strong, it can actually do more damage to the tissue that it is trying to protect than the virus would have done.

Thought question: Why might it be advantageous for a virus NOT to kill the host organism?

Review Questions

Question 1.4

bo00ypUPr3H817s1+3As1NAZKqhIMCM80diFJqyes8GVMtBzASWrjidO+5iLT7WmjIouPAgeAr84kZ7Xd20Otb7WDo8pnQ6i9Jv/PDweYdIjGkvFxSDfYFwizUthRHCB
Correct.
Incorrect.

Question 1.5

Choose the molecule(s) that may constitute a viral genome. (Mark "yes" all that apply)

a. DNA PcjeiwlDuBLi5zTg
b. RNA PcjeiwlDuBLi5zTg
c. protein sjkhLuRCQ4SijoxQ
d. fatty acids sjkhLuRCQ4SijoxQ
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Question 1.6

Which of these structures are found in viruses? (Mark "yes" all that apply)

a. nucleus sjkhLuRCQ4SijoxQ
b. ribosome sjkhLuRCQ4SijoxQ
c. proteins PcjeiwlDuBLi5zTg
d. DNA PcjeiwlDuBLi5zTg
e. RNA PcjeiwlDuBLi5zTg
f. endoplasmic reticulum sjkhLuRCQ4SijoxQ
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1.3 Driving Question 2:

Driving Question 2

What is innate immunity?

Why should you care?

Most of us think of white blood cells and antibodies when we think of how we avoid infection, however, natural selection has led to a much more comprehensive defensive system, one that includes both rapid, nonspecific defenses (innate immunity) and slower but highly specific defenses (adaptive immunity). Between these two systems, a very large number of pathogens are defeated even before they make us ill; many more make us uncomfortable for a short time but do no long-term damage.

You know that exposure to pollen makes your eyes and nose runny. You know that mosquito bites and scratches leave red, hot, swollen marks on your skin. You know that your stomach fluid is acidic, and you may know that your saliva is as well. What you may not know is why. In fact, all of these are instances of your innate immune system protecting you from foreign invaders.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Describe the role of physical barriers in innate immunity.
  2. Describe the inflammatory process and its role in innate immunity.
  3. List the two types of phagocytes and describe their role in innate immunity.
  4. List three body fluids containing antimicrobial chemicals, explain the chemicals’ effect on pathogens, and describe their roles in innate immunity.
  5. Describe the role of complement proteins in innate immunity.
  6. Explain why each of these defense mechanisms is considered part of innate rather than adaptive immunity.

Infographic Focus

The Infographics most pertinent to the Driving Question are 31.3 and 31.4.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
cBRbaZB8qDDgPcZRIZwZ+vbJkdajCqmWChgFyrL/Ehhr6CW2hQb4z9yroh4ukX0ctESeooxHPNDFgiMRLN5MzLWiVe7uGSfEuI+8iL3VjjgUSvVNdNSbnT0Bz+4EWOdBPK02gjMHVkuJF0H+Kgdv6/XMx4zFIUU0+H/9QrqU6ikQrvkx3oWh972eo2Y= A type of white blood cell that engulfs and ingests damaged cells and pathogens.
IFtQiSdzuTjsnfD9v5GmqVjIrNq81JoZk3x6v0eWqbKNiAELwOYfMsgQBw6IQBcw8lxjE2zRW2dfCixwlKHxROO6QpixH+VPr+KIey2UF22CH/9ivnEViQy+j0XOMamrqEPws4p6G/0DAthcgFbnZdLjEodgtNyvv0ZmCH7dg5LfzH5DqeL9f6aP4Hk= Nonspecific defenses, such as physical and chemical barriers and specialized white blood cells that are present from birth and require little or no time to become active.
0ICkSaABP2XjD6ku+nWqQYAUU384sJ1tVMpZfEo5BH8SEqKGEqKy/+Evmc1kJQhlZ0TPGLa7P8genZhS5yrv7ug7VTiLDtZ/wGYd/VaqrN+oCgbFMpQnaJ8mUPH7TqhtUsujItXT5sgWDyuS0WlluIditsSZQ+mKpRrj1w0HAQlLhFHgjJdwh2IfJJw= A type of white blood cell that acts during the innate immune response to find and destroy virally infected cells and tumor cells.
+GXtG4HI+25jpL8kaA12QmIxDO6E/o3V3fAnmxxpLLPbwXGXaxiWeVlTfAOHBEppL60bP+ZtvsdO1qvqWVqVaV2vCBE3h7ETr278zdceSJmVWWoXwhF8/FKnUaAjdlkGau+Sq2Irz0L6WK0zjjB7yM2Fv7lg7hO4JSJlgF8dVe1Nb3aL3vQfWx5bgkg= The resistance to a given pathogen conferred by the activity of the immune system.
gTFIXHaf6WdMJDboVzfkhP7WfX/3/l8EsemIHzsdM8V5yoODr+CLlSa2EIsQlLIhOrZR+mCrAenzvu4GploAr0UyS0h4w38lJ2lWuMKG0U2sBzxdtOr/t6YKYfFB3hRitM3gsvnemhy7/UuGDoMLSuaEHq1FrszttAaigRrwSIe8347jnU6pTmT2TrE= Proteins in blood that help destroy pathogens by coating or puncturing them.
HqYZIb2yg7a4EiYT72xlOHjyzfnlj70csiIAjqLxHmrA7AKV+XXvpPRrp8K/sFZryg0JCz2y3nAOptEqZfvNjms5iItDV5ArLt5qOwMJ4GDggmDdUIyUu9XKWTd8O4kML2yw9L/jCBBWXf/rh2m1XUG3QgG46mrrWCMbE2Keawg24jDa9Pln+CltLb8= An innate defense that is activated by infection or tissue damage; characterized by redness, heat, swelling, and pain.
ayVqNQ9DThiGHGE8wNjH1Z0xXdwo/6z5QYsBKxWsatzlnxfObNRCfZ/k7JQMzpt2aQ+qKjgxfby3ylgAhXQlcMxN8jB/G6NBU4iHW1xLxQXd96y1TiLP7Lo8qJkEjRfqvFTm/V4on9mT/4jOoNuz5I1UzeJ93rVLGWQe+zBiBmM8goK2VggLl6X07FA= A phagocytic cell in the circulation that plays an important role in the inflammatory response.
JS61TExD4y+LwxvIUk/ICa4FLXydZC48hih+0YO5/C9ptJX5iEsACz5Bu4J96T32JsUdX5qA2nq0M+6gWgC0rmy1+cy1k1Evwj2ob5BhYP/sWC6W9aUY66/gYH5XsK+6WEE0IkfkbC1PjOrQp7Lf2AAnWUc4rwlWW8hEHwwqGiW8MbuVt2l+QenUeV8= Antiviral proteins produced by virally infected cells that help protect adjacent cells from becoming infected.
kEtQp/CfXcYt/CXuIs2fpGDG2PAxCZD5MZzJb/9hUzjyBeNZVUOETuQX71xQjrRfcBddcWKgllxlw04YVOMuNueLN/kaORlqBgdRYruRvV8ysrxGM5WaUxPDAODamMWFkuBm5onwjcvDxQ8esRPjmA42hM4d+eWXRD2uGu/rq5IqfOkx6vw6V/yW6Y4= A molecule released by damaged tissue and during allergic reactions.
q48/hw5GXrM7RVGSLUbcP9NP2AdfC/INJUZeHNXSJbYK8UfvorlRwgdf+hl984HRNs/Co4xxzwczzCCM+7jplA5aafFLMKmtpfyVpni4AvF1zD+TaLfq31RI+QqIU4DNXcyk12750dKhYYnq498lavQDxLnncgFV24UMAPA2oCN6sR572pVMfL4OaL0= A phagocytic cell that resides in tissues and plays an important role in the inflammatory response.
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Describe the role of physical barriers in innate immunity.

Question 1.7

SEi0CKX0pe2VH/cklgBAgQxahOuXRj9wPLroKLc+B/tZUf2ys3Xu8hgvcMtppnyznoADCjXynoMnYVkhC0Y+ymAE76oErTFADeK8RsgKO/JdHZQVzJuRkDody4rhRweQ
Two major physical barriers of the innate immune system are the skin and mucus membranes. The skin prevents the actual entry of pathogens into the body, and the mucus membranes trap pathogens and move the invaders along to be expelled, as when you sneeze. Skin protects the outside of the body and mucus membranes protect the inside.

Describe the inflammatory process and its role in innate immunity.

Question 1.8

HD+IBPPI+KapgAluBPbjBU7uM304qjaY4W9bhf/rwpyW6GDvEr13GiMtIEKri/3TjPfy5e+1L/KZ1OFU4FrwZdOXm9Y=
tissue damage and infection

Question 1.9

4d8p154ADMCPaxeCOKLX+EfIHsjYHVEDq+VjFwPXYUx4nnv45UeAaS8hPaPg2lQNGK4QlZDSmhJ68Q8waE0yXqQrwgr27KcFnURhKXzn7pCAUycrDIPbkaOfQANW7qomuz0t2zYvFgIAeEzgaLnL8QyDd8BpxaCbXfhowYH3dIq2hZle
  1. Pathogen gets past physical barriers of defense.
  2. Tissues are damaged by invading pathogen.
  3. Damaged tissues release chemicals, such as histamine.
  4. These chemicals increase blood flow to the area and cause blood vessels to expand and leak fluid to surrounding tissues. They also attract white blood cells and clotting factors to the area.
  5. White blood cells engulf the pathogen, and the clotting factors contain the infection.

Question 1.10

pdOmJW9PEjPjx7oMLIszUQ2h47780aTtSl4fGR4kBRhcNXccVStybpzz1wky8Uidx7TAcNF0b2hxhGbDwftLchKnsGn9OtyXPZ2/5g/ho7Q=
Increased blood flow and leaky blood vessels cause the infected area to become red, swell, and have heat.

Question 1.11

zSeINfigw/S2IXRArNxU8vwz7X0KSFPEaKRUw+9FhutUlgXJBavBaVSKq3Y+9OQ0MkMagZ32MujSTPE6xwFBxvxhhzg=
It prevents the spread of infection by containing the pathogen to the initial infected area.

List the two types of phagocytes and describe their role in innate immunity.

Question 1.12

ayP3x7yxxquF4d0XpeZq353XTZhOSJdG+eyCrD6Fcvt60ARzAD6IpUpB68vG/+VyDmQ+JaXo9TYd7K/z+XyhSrwCIucwU5ah
macrophages and neutrophils

Question 1.13

VZVnvx79dua1WBZgWaK3t1YQjMLdIO4lnX+zRA==
They engulf invading pathogens. They can also enhance the immune response and help initiate the adaptive immune response.

Question 1.14

bnhxXbJmQZctfZf3Jp/LKGJEHnELuf3RrTrkI2Nmg8yutUhqyq/k9x7rf24LYK8cVBHQWWoiPwZAITYvyVa2B3mz17XucQE5OjfGl0bvGyQ=
They are considered part of the innate immune response because they are already primed to function and they nonspecifically engulf pathogens.

List three body fluids containing antimicrobial chemicals, explain the chemicals’ effect on pathogens, and describe their roles in innate immunity.

Question 1.15

H+pq/3BUaDxZ9ofhr66TrkHaDIinOaxBMbNJoXaPovjmocEpU15suBsMUCpdt3KMW03gIF4+JGQnFTH7zOnI1XrUYbaynzVipDTD5L4vDll0VYtXmpOYNs+JQFuEoTI7CMsIg610/LOQ0yWKBW1g3pGBzL2MYpaHDrHgazqCMqhmNMf4bt9676oz4uPmQVazKL1MidkBbzvDqomL
Saliva breaks down bacterial cell walls, causes cell to burst.
Stomach acid kills many organisms ingested.
Tears break down bacterial cell walls, cause cell to burst.

These fluids have a barrier function in that they prevent pathogens from entering into the bloodstream or other internal body tissues.

Describe the role of complement proteins in innate immunity.

Question 1.16

HtcEwJiClsJWBwEjgO7uQ3SWij1I97Hqgo11lenoZfF+ygWFia1Oygosw94pK1YWEl8RuyDU5GF1970dzeHtsA==
Complement proteins can either directly or indirectly lead to pathogen destruction. They are capable of punching holes in some types of bacteria, which cause the bacterial cells to burst. They also mark cells for destruction by other cells of the immune system. We may think of complement proteins as a spice that flavors pathogens for phagocytosis.

Explain why each of the defense mechanisms described in these questions is considered part of innate rather than adaptive immunity.

Question 1.17

kvQ6sSsHibRtMWiTcw9dRE8K524w+LmhnsUvLFOpEiZiYpiorR+dtF4JeoT7Er3muNSXk7PVgI4ZdUlot+5kjaXxvkUoY/yxaJcxai+YqcU0MOSZXLn4G9cFgpk=
These defenses are considered part of the innate response because they are always active, always ready to defend against pathogen attack. They do not have to be activated, and they are indiscriminate as to which pathogens they will attack.

Review Questions

Question 1.18

f4R75SKCW9m1xHSx3lY/HWj3JUMFLMCHx3jpy4zjowdEWkHR7jmkrbLqXcj+obhSHeipRM6dnnQqu1KBZr66l+ssAEn1qV0CWUHdoKgyqrLYfQ6cOdN1LkCxRJfN9yrEvXMJH/qzwjJDvd6WUFOqvthZsILVokd5jhZvioU1T2PdJS4grz8XUwxJZh5VitaDTJ9xeg==
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Question 1.19

FDkRAuVaeEQSWue3ztHUs6r2Q6pY3RALgY/mksIrcGxrpd4QCWUra+YCJsQInsHcd19iMuGJoInH1NINJuTULl1mokvzpwzdPMGZ1y4NPZmd+g9i9Ny/xW1Dp8XPjWrGjA7vT8aPRJrd0bqL
Correct.
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Question 1.20

B+Zub2eFquOCxmCv+wI7HR2504ksZ6DFEVo4pQ5WPyo0WRTq0FR/812ocloQhBenFjVSF9ACh/BH8U+oI5EM7JH2jK+X6zfhZyk7MoP6tTASZdrd0i9UEd/jONQZ5ywG7I7X8Z3WDtl8BqMDpxPGYLc5a+K3Oy22QYW/XPZSfL8vC9e+I26RA6NbFdfQOt5eAly687UpUuLQC9ab+2YGPpS2s8qK91fb+IDERQsmIWsEBp1tC9VzFuSlc/48wolbfWjdZS5L6DDNfeCQhzbaj02n4I7Y8XS3F8BiEwjF65bqqFWb3UgbCTqi39YS0VLNU8RapKVWzYtmDccrujOei3bqlecyylU+xAqRV1CvVyST/UQyCOw8k4MtJ1TxOrpU3Dpej+Y4QOOZFS23
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1.4 Driving Question 3:

Driving Question 3

What is adaptive immunity, and how does vaccination rely on it?

Why should you care?

Many infectious agents have adaptations of their own that allow them to evade our innate defenses. You experience this every time you contract a cold, flu, or stomach virus. When our innate defenses fail, we rely on our adaptive immune system to destroy the pathogens that make us ill. Our adaptive immune systems do more than fight specific pathogens, though. They also remember those pathogens and prevent us from succumbing to them upon another exposure. The B and T lymphocytes are the key to adaptive immunity.

When pathogens invade, they can be present both inside individual cells and cruising around the tissues. Fortunately, natural selection has provided us with tools to deal with both scenarios. B cells produce special chemicals, called antibodies; these are our mobile defenses, able to detect and defeat mobile pathogens. A single B cell, having detected a pathogen, can multiply to produce an army of plasma cells, each of which may secrete up to 100 million antibodies per hour. Because of their specificity, antibodies are useful tools in diagnosing specific diseases and in many kinds of biological research.

Antibodies are great weapons against mobile pathogens. If pathogens have already invaded, though, we need another line of defense. Infected cells have mechanisms allowing them to signal that they’ve been invaded. Cytotoxic T cells recognize those signals and destroy infected body cells. Although this means that we lose some cells, it also means that we reduce the risk of many more cells becoming infected. Cytotoxic T cells are also a major target of research as possible anticancer agents: if they can be programmed to recognize specific markers of cancer cells, they can target and destroy those cells while leaving healthy cells intact. This would be a huge step forward in cancer treatment.

If you had chicken pox as a child, you know you are highly unlikely to contract it again. Your childhood vaccines provide long-term protection against diseases that are potentially fatal to children. People over age 65 accounted for the fewest cases of Spanish influenza; researchers believe that these individuals likely encountered a very similar virus earlier in their lives and had therefore developed partial immunity to the deadly strain. We owe long-term immunity to the secondary immune response, which takes advantage of the memory B and T cells that develop the first time we are exposed to a pathogen.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Identify the components of the lymphatic system and their functions.
  2. Define the origin and development of B and T cells.
  3. Describe the process that leads to the production of pathogen-specific antibodies.
  4. Explain what antibodies are and their role in fighting pathogens.
  5. Explain how our bodies develop immunological memory cells that can produce antibodies to an antigen they’ve encountered before.
  6. Describe the process that leads to the production of pathogen-specific cytotoxic T cells and how these cells fight pathogens.
  7. Explain the relationship between primary and secondary immune responses and the practice of vaccination.

Infographic Focus

The Infographics most pertinent to the Driving Question are 31.3, 31.6, and 31.7 to 31.9.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
vWC6w4g9v+3/hciUPNkWmRpiNwwsFBoWUQCKmI1K6J4knDcfahpKNsV8huNluTMmCB1/Jr+mALQCqdFochNzTSJnv5xAhvIFafiE/HnO9wF9aeQ5f2EpH13GuROTtHMNri9JTNS4x7QV1qaQNcibq8nHPeQVRZH0w2B+Ac3VY0CzbLlLDzN19MNynzvNZFghfz4E1CDkw42saxCaF93aj+0jGPzBCHghQt6yiuXtUDkz44swJ+NREUzR01AsphhUSMPzhUo4VLs2JnaGAfC2gQHoacfa7HaeWtTH/S7b60KxI2KqnTPc36dVSGsPsr9iTSUkYetnYyrrvOpDrutXev0gJWzvz0MPRojeCjXhda8= A protein produced by B cells that binds to antigens and either neutralizes them or flags other cells to destroy pathogens.
1VpDxaQZs0RKM392lV6SbpFUuw9ZNMlxi4rIBYs6NHuwkO6B+AOesEljglkM7Zu5ndtZsZvOJ+ki2wms3wFjpuMlj6swzvtDiTYfAnoVBD6g95p/F5oi2v2j603pBzb0cKUfrIwy7DaWwk2w1V59MMNF1/NSdQl3SKQ5IoEnuiunc9zBbmHmzW42P7f2XamvtAzmkvImuszAIwN/QUz3j/wb6QtiVrnybwhXiLHD5X24R3DTrJWBd14nfmyers9gYUi0t45CbTa39ZwMqVi/GP9nx15wxx6yKO4rZFJqDI0BqyUaHwv/zuFPKyt+IOWoKHG4uWuZZHx0bHvX7cSg3jFCns56oFcu37ycnd1dCQU= White blood cells that mature in the bone marrow and produce antibodies during the adaptive immune response.
wsMma20Hb2y87hk3S2+/7n4AMALy2PVfp8w4zTYn2Xs6ormDX5Xed1ufx7UWqjTfoIVABMqxDm3dM5pbH+kI9yy87MhnH5rrDnRMUJMZsPrXxRwEPxfWCk2iS3D4grulYaZAFL60ZxNAhpKRZ6K4FiC4n6lCGSlsaEoPR3/G+U34631qVw43K+T0Dqk6fd0PdiFRdSkVZI7oskl83K7m635qmFf0DCDJMc4H3YIyL1hF3xA5KnAayiNM7gYAu5BIKn/q062lCtbUsEXIiuvQfHHsDwm4/YwB8ErglMrNRNFjLhtPpsuo42leyMo8+73/k99ihwMqNjZS7j2H+TEXEldnV1oQGFOdKZ9JCegg+fM= A long-lived B or T cell that is produced during an immune response and that can remember the pathogen.
7yrhSeBb+SV2noVgnadAR3X4nXhOiXZ3WdGrLw/YIExvkEGleZJmsnXWWrn8R6pu3GVW9vQNN6/o0XpMLPqFLv9elvkQcbxVnQbXXhXDzG3ZlUiomWImdLtIGQp0pG5Nn5hgFBI3GfOgrHK7i5yGOqSdH/4gpA1CSqyFU4St8gdxKjUihSJN4x3kr8DE3HN3lHcLTc2P+UtOgh9nwu5QfD+dbd0QBFyDTYVeQRbC3i5nxZuLtlcgE1w6BQ7GDaiOMD25Ll2eDQn8CjjaT3u0F0oglKKm85v4+XWmQV50aouFbzq7vSqVqnWKzsvyZxcFjnc4/cwgpC1m+jJ1RS6I9Ii8nkN/F+saM3amPZwDjTc= The rapid and strong response mounted when a particular antigen is encountered by the immune system subsequent to the first encounter.
C9wkYWCCCp4LBOrRH06Pe04R4n1n6Y6OHezSrubTzsPfJZxZ4BHcfFdpfdbGLyzJFigB8RcvJoE35Fnwt8RHgeSUb9zeSttRbaidZ5Ee4szdlrAlbY9VhFEPrhw436MlLYzsWGHB3CH5WrigfIhSbtdr9biKTv8qYxWoiNudpdrnKs2odrEbq2WmpY8c4MCMQSftA/YqajjKAg/b3Md5bnyM6Q5yAKrADKEQ6qtaXP2bBr4wBUs9FvmWSTzuyjeOf8BAIVcvTwQOeYJRfWcKnA+63Ty+66tmALiug0odlSxMxUTS5ZQrgGz9ZNFsH1BsbcTyF/MpOFmDRAdMgRoVbLOs5IttrsEExEd6Oa6vFJw= White blood cells that mature in the thymus and that can destroy infected cells or stimulate B cells to produce antibodies, depending on the type of T cell.
y6uavyhIe83WGK7gTi3ZM4YgUU0w0+rpA5RKFT/PkHnHCLRebEKE/ViXKsWjiYMg5faJpaJspyAlNTA+XO+4TFXEDdvU0d9v9lkDfRC2owATA/iU97Fh+a56dkYZQdW1S/9tvpAp1LrEG2pE8Tx6M3YkCZZou5gw3npZHXTtdRK11Lt5tfHbP0N9TR+mnqmJvVWB+E0HA/TKzC1vUIsKeQBFlF6Efxpqv5UUJsM5JR+UTrEKEH2O+AEw1Uawjpt237DRf/Jvr57E6dmUnjmkbYMe+obF1I1POtw6xYORU8rnyI3LjwVVWMk2Gtx4xAVQu6f6anyabYtGQQnXRTEqFFrhCIL1RkcKhD77EEJF+7Y= A type of T cell that destroys infected, cancerous, or foreign cells.
Ivl9SC3hvoX6CwN9wrm0euMmFrXGz2Iwc8QVrwTAMBzpC5r+mvoV84gwpuprSYpd4rTMHYBqeqiZVJkLrCEBOZq01apz6ZJ9bMAGLEml7r0ij8FOoAqxlZpwhzWFHyG3rpFV9JJn5RZhxygBw39Z8c5oQLZh0Wz/M8AqkjvckJhjn+2QhYiZsos//n+ayQFcicxnlSP+IovJPyr+lvxJl692EnakjAe6iUSSd6kR7vVwF12sAgbKydYSK+G857lY2FmnobTtkLzGqGHXm1+7+oz5anuybXMfoGw/IRau8y7IMrC8KkeZwlrk0AqXVBa2LLWyNqbhsVerdFF7odyKXkt4BSUcN+xM0wyujVwEM4I= A protective response, mediated by lymphocytes, that confers long-lasting immunity against specific pathogens.
wa9+PR1cHtPsEB5egRSWOSHRE0Jn2/Ec3I3v4XEcKVu2MsY1VO55EALGGFNlSWNVEiCJfRJcwT300yL45PrlnSdT+S2LW7E/ZBvp4Xft6wBaLFEpY4aCjBOi5VuLqReXefXXTwWA//DVXQmWwZhIHHT13M15Xk/Z6OAOwrUWrqT754w3TRcojVy98aIbKKWi3rsCSLCq26nntc9CQpYkTRvIU3BO4a4IJU8xae3XkmDzWnuiMxCtRGjXIkqjwnmO4kApIO0QTHVjszPwgCJlIL1Uq1TKGzloFNyLVZ9CewON0i210K775WGVosuFYrnccWGMEHxVzxG2uVHyfHLYmTnE7SUZUI9cZSJVlhmXwZs= An activated B cell that divides rapidly and secretes an abundance of antibodies.
RVA5MBUq7UcrwQYrVyE53tRMjwB1Nwy2GAXhEMjMbvi05Kmrh7ZjHwPf+huAIugT610auN1AjiRu2eu7shK8o6gGMMJB5uU9AVPSC/hTmMNt9mHBiSOfLpdjk+o5vICx9wKbVZsMT/QcBy7RxKuNxdE4FCe1bvD7Z+pCEwf5kskSymRbKwZH4T+dfGPuyqObyYjs//klMlf+UDXJELwgUYdtoOgYrJdtn7E0R+PCyz/TgSDxnyy8m93cukDSQUQw8kQV/wRjVrmvoDeRkDP8dGmi/no/rGLhqJlCwwNJZRXb9T6LZyGB6E9GP0h4bbH2IN5+WprBlPSXSM3lqxKHca1iIn98wNzL2H52FmmKJiE= A preparation of killed or weakened microorganisms or viruses that is administered to people or animals to generate an immune response.
E+OJvNhPBKiswBytrjaWKHjSeQHHzrfvE7OkK0wAgKLpFuhaS8ORcO5mpCNyTRbFfA0UYP7s+t95KAef9gu9Et+TnxvcUw+mKKmA3ho0VqC2IdVAI22m1nqsnSMG9dY+oMG4itm/vKXrIpZM7p6ii+EMjRsJNLxeWQOCAyI2AA7cxYpcwgLR8JuR39ubz36l9KG+qBCnANp04XLMDKLqxq+qi/NVT+YgoRpX7quYEzIEBo0M3fNzvk0JFCLA1XqB9Zm4g2oaQqtpYICJ2fvhSkojkNCzoneoYZXTt707aH2x/oYxDnAADtNU99Jpvt2E9Si6wq5aax4IR2Fqn2CjR9TVR2fGU8LxGvnkKhSEJH4= The organ in which T cells mature.
unSVBXryC7m8F3YHSlpPLaL9tMCu83aro1elXwYCZtPDguf5/XJ1+rc8sFZnZS7BRgJZ5933B6s3hNSboTh2MLMOJfrpduoCkvd9HzzpkupaHtQnj0b3NsT8A43tW5X7/F83hdfKCoefXgdthl7ZLRUVu6XMCnDmGcmqZFiWyyEFmG9PSstJXgWYTHSZbQJnOLfTF4N0U4luH1ejbNoV6giohORRzKY/1e8ES70TkbK6kDiZbCZjeHbJp0P2wmG11cfnKrWwhtx14ESPJIEd5Ut0qZaP9CiD99HssqlMOQZnCApc6FWCZXPaGbfXTJaMHzXV87BpBwTHAgUKQYppuiNwNOW78dvcOyen5fGlpM0= A misdirected immune response in which the immune system attacks healthy cells.
jPS/6mGsk7/9klhqhB7+fE0HJXaYQ9si8VT73kFd7r6ldhJlM3NKaT7fQDa5f5mM+yZu/N6y4I4FW3ybd6OsYQTuMDCarIESfYDo7s5MgTg3WehUoFAmGb6VkOsbAMUYrrbU6baJP5QO9Lk/X5dYau0IRdwUs8dgYB2UYcwlmu5yw8Q1hTB7/oWVRCQz25m+R3nfvduHxih+3RAqQJXhg8zWaTPpna3eByhEj8oR4Pn2Zso3vTGATfuF+hX2kVgCz3vYtHVa9Hv4qhMYzI5YpPM1xiFq3tZoTq81QgVfqTnA5dvroFqeUk0RMkBUoj8VPeQ8tQeACxRbiJaNc6/nJUcmfHsadaoQhsRY4bA0wcM= A type of T cell that helps activate B cells to produce antibodies.
mCgKa926oR+yTyHpr5i/6nwAG4FUnR8wePaOANGymE86dw7Cgplmwc3raYJYquRz2ZR848bGvCpaQpIqfuiCwkRoPcxZvjpSZCWfbuoUaAmmlpTeq6uYj1fGsjTYItDlClAB2nbxvDDbR07Nt8NvhcEzT9tjkUhWtK4p82/L82pSyl4g+NiEmR0SqdmUymM/BUKst/zq1nluKKb9kQJs0rxaQuxdidhpP1AMzEV8XkZ4PQcEKfLQysI/DJMG0g+p/cQZRMdA/3uysq4enj7TkTpvYVsWh6iLJxuWtlGDrVJMBKKN+NVumrwaetKdZC/SIkRMcj4xmlsaM/RmMZUqtG+4FwurPLcCN13MPZZ0It4= A specialized white blood cell of the immune system. Lymphocytes are important in adaptive immunity.
lvLU1cYbwI3WpYqR/UHEUI8kYKGPL826k1+5Yft6DjTgA4ZSHpuYFATNNrSws2Xf0HrqWO2b7vtTSPr2w2lpjdGkydBPx3Ng6X7C/h03Jgwz2uudyM7HV+Ml8HSALJbNerOH5LOrKPGUXKILINI7b/bECg82mrTnn1p61yvzbaECJHulZQlclYt4rzcw8oo2VCNdlUvxPcTPEoRxSspToL00DF9wIErpzre9zfUOCjuk4bxAqIiYk/fP7JSzZPTyvee5rAIPFf6A8sb5lRBqzi7Y98Pi7zXxKMbv/gX2Dnnd7KMzKBY2abVy7l7qjdB5O5v9N7LwPYcQZ42HnQL+zL5CGOli5F7zo+kqmngahm0= A specific molecule (or part of a molecule) to which specific antibodies can bind and against which an adaptive response is mounted.
HbKpAtrkD7aI12NmZ1H8bE3VTfzZUQ3cOe+QhZ7Uh8W0/Oe3HJy0zs3QHe6W6G6pmhn5WiIGEHRvaIymelq1hWWF9G0treeWfnAjnMNPThEva2cuWU/uGztFlL12JQAGtf0cteWqUOYlMNE8H58RoiNDUUjJYviJohwLV+KoPyOF0k/C9A3+/f843Mk8PTJsrGgMi4WvOY56eDlU9pA8nfalfEEegehkXsxE+ucOBQ9gSG/wLXTrj+tf+wAhR2s8kMBoG5Om1CKhb8pPhnnmTqNwElyuJ3gFlyNxNWEbRWficI9ClkmunKWjPbnZcKQUnzbCm5YG3HhOx+sa0kDlNjVzj/CLg7C1utxWU/6DdNE= A misdirected immune response against environmental substances such as dust, pollen, and foods that causes discomfort in the form of physical symptoms.
hdVyWT+tWiEIVGPQ1V6gZCv71EFrmzEh/NCMubJ/j4xBIk//qVTMhgO6AEby8TPqhhz6RReHk7Bzyg76kMiqZOWg91VQJpB6aeX7Xt4zroZAoPt6HW8Jv6AUz7CghMfYp3TQfAlvh82Atgzb4+FF3AFDZQGj9XFBgwz8buQLOxcxf6ivUtBWsHK7nE0wTLNMgaUfmGI6Ou9KDQQJr/Akdk8cM12Z2s/lyrTDM5NicTuB/ln84mul0mT/3pDeeGKCM09B9BOfD/WKmjxpiAgvMBOhNTC3x1xLMmxz6x4frJK3n+KJIZ1QqYS2Spud4oyca3h9FGgmUC+EMb24yYBkHq3mX1Brt52MBl/3a/hxDIo= The type of adaptive immunity that fights free-floating pathogens in the blood and lymph fluid.
aOOwtVe+KphUY1YjMYn150tgI8SkvLH/B+ZJgO3NQBBW2rsycE8XtkttiIWO8h4L9wxSR3l8lPs8vCSyZSB6eAm+rs674qWgTesEp8ueuS3DEb5/bfrX4jfpkA1Tz5Ls3kkpNAfy0xRqRtNUl1a5DugkMlmNqeDVHpCGZAsui0vq8q2Oi8R+fH9t0l2HG7V2LkkNVsfVay9RpbMWcqj4figeisDxt137VfJ/N1y0Dx0aDpCA5LRLrEZE3owFidOyGYdCfYOij3ElS+Qkncj3hY6aVwm00TIfXyyUJtIQUqUkBCqeSnifOvzhbPYlRkldodLRhR66U3azCpxzDwFQiBwpv4+utJUb0ecix0kidnc= The type of adaptive immunity that rids the body of infected, cancerous, or foreign cells.
yOP+mksADA/HtFqjsCtqgsqsrB0h7+hcMeYvf8FmgDLgpBmFwguZzOpbmKtUtk8tKmB9HYqSjadiLMg+WaGCo0nRDgu9z8OPLgOLoXhy1P3WA1fTgE9TFPh3Y5JOG0TjwC7mjaq2IuiCgZOZSNVg1BosOM+1KIpVk4MZ2n/r6koyrXcjCPqGG5hQtrR5Cje3MycD9QcCl0kTbL0MFmPFOKE58M8vUWheTx10H5pmmBpN4Bqu9ynYhDQKo2MLFZG5RSfkOqjMrme0V17B2n2/MNXHtioJW6O6qi9XUcZyPXvEMReXH3H+RLJV4GlaAXzFxmUX0CSlUn4ALKjaLj3dPQLGJ239omzsiTzpPpZi+cc= The system of vessels and organs that works with the immune system, allowing B and T cells to respond to pathogens.
bshACHTJNdIQyP9hGLRM0DL1BP/5VmwzNl1GzUxRdbNv8WkRgjDVwumzlf93lMEJKKQj7H9HxLBmbHVWcSu6yCiS7bY9wFO9Ziq/rvZ6aXEeYZt4fp4vJi0JXRqKDH8uGpgD9Yp1+XShpcA3T+S73MRb2WFzNk1ti2D8FsjPlOtWLwSs3+9zaY3AlsFnDO7W0EPT7N5lntBfmaOQJezuZjRctFx0ojNMM54WYcbPXJmxSLyiSBliRsFL5zzoM9+DEZQsaLfNDO9i86JoAiXfpXtRn36aqkSnrOdaj8YVCIcMDMqvtSLrLl/pTNWhk/oM48hc/qUNTBytKubSX91YccpVtsozdx+WQAgi52tWBYw= Small organs in the lymphatic system where B and T cells may encounter pathogens.
/9HMM/hr4ZGNyJDtHSzn/NFA0/iaZB7lvS0StQlnufl/Mt/uM5S/rWGvjNWPXZao9trL/YO8RbeLXt5VkYOuSnHx41xgyIZiE0dE0g457wR544VFPEuHp6FefO+feoNT90j/ReshprXs846q8Kbz076Mz8iDeYI9Onrok6uFyjPD5oCnvFUYSIg5cdDTsBj+wSQTJq4h/MCN7ndLYhBvoeauBzbhulxSNho7sVsvgSzoIUYvRE36ZOw8ZKT9dvsT3O0ALeCp2Lny/FGtbCqytXkIPqFPOWeZxun5e7IUHyF37XCxzhrTSs2cF1qthO25wzdXCfIf+lGaFmx4Xb9bBva9IJjsmuxobhkZtxWvWJE= The adaptive response mounted the first time a particular antigen is encountered by the immune system.
Table
2
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Correct.
Incorrect.

Identify the components of the lymphatic system and their functions.

Question 1.21

+dVnuE6CJMrOONOdYQ8mrPbV7se9A9MzoPU02UUdY6QMhM1gXfOfCXtmoYDrZjdzP9sVEi47gHX/FdSccpyWetUo7AWoiChyzPhyUbRthxh4XFVt/GJ2A4wChturtuj2EL6BklGEdDyMTCtFqIVR3P090XE04bSx7j0RakaZ3kzbDisJb9EHpd/tsq/IVJaeupo3JAjN1fk=
  1. Bone marrow: where immature white blood cells are produced
  2. Thymus: where immature lymphocytes migrate to mature into T cells
  3. Lymph nodes: where T and B cells respond to pathogens in the lymph fluid
  4. Spleen: where T and B cells respond to pathogens found in the blood
  5. Lymphatic vessels: where lymphatic fluid is drained from the tissues and so it can be passed through the lymph nodes on its way back to the tissues

Define the origin and development of B and T cells.

Question 1.22

Fill in the table.

Type of Lymphocyte Originates Develops
B Cell a5T2+/GQLVmbvNqnugiDytLlYdv56nySaPveHQ== a5T2+/GQLVmbvNqnugiDytLlYdv56nySaPveHQ==
T Cell a5T2+/GQLVmbvNqnugiDytLlYdv56nySaPveHQ== soyyG/OO8Z0LNaYh8RefrTbLniE=
Table
2
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Correct
Incorrect.

Describe the process that leads to the production of pathogen-specific antibodies.

Question 1.23

shPI/n4Zhh+H0GT8RqSw7E4ASnQyUYmcd6Scl0jzd9ZSdFIXEAaVOsNjzRC9oqRj4+G9mA==
B cells

Question 1.24

COTrXcOPhB6Vy2zpbZ6bHOwEqgKtEzAotMGWuERzcZs1dN3KSxTksX/yJoYAPNM5alUtWWLiFP0meJUn/eruTLmYUxsrszNzQX+FUXsbppbsFh1eKNkjW3wzkH+Kww7qkRw89PZ9az0ZsMTWQaxikRGkO2jYzCPBYH+xrFFxePgYcUdiTjvrYX4vNp5JHlXrWlDWcg==
When a B cell recognizes an antigen on the surface of a pathogen or a pathogen-infected cell, it has to be activated to divide into plasma cells (specific antibody factories) by a helper T cell that has recognized the same antigen. It’s almost like a double check to make sure that the B cell has recognized an antigen from a pathogen and not one from your own body.

Question 1.25

YcFU8TpRdWMBP0m2TLX38qXxvfnXCHC4ou8J2+VAm8OdQtzch0jJyQWTcj+Uo6iGxfxty16aj7xQ9hDo0R6mGLcKL9JlcAwnu75wrq2RLZpwfGTp93r2hQAV4+jWE7AI7K1AGmHWCrC5YB/nOGOxGYysRwWmG8wwFr0ww+e7ign1MVyVQjVh+rwJ+nM8+Q9PmVMTeymgSL5qNxt1H81C96U0yPKqXBd5fA/OpPLk1I9libJ1v1YJRk8HNHecyw9WDBGPuSlnHsfiD7u3DTdMZBQktg6FCafTSwLwKYiPon9H0DKbBo6ohw==
  1. Pathogen enters the body and gets transported to the lymph node or spleen.
  2. A B cell recognizes as foreign an antigen on the surface of the pathogen.
  3. A helper T cell also recognizes as foreign an antigen on the surface of the pathogen.
  4. The helper T cell stimulates the B cell to divide and produce many plasma cells, all of which produce the same antibody directed against the invading pathogen.

Explain what antibodies are and their role in fighting pathogens.

Question 1.26

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Antibodies are proteins that are made by B cells to help protect the body from pathogens. There are many kinds of antibodies that can recognize many antigens on pathogen cells or viruses. An antibody recognizes an antigen by sticking to the antigen itself, which typically results in the pathogen’s destruction.

Question 1.27

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Antibodies can act as physical barriers to or markers of pathogens. They can physically prevent pathogens from entering cells, and they can mark pathogens for phagocytosis or destruction by complement protein.

Explain how our bodies develop immunological memory cells that can produce antibodies to an antigen they’ve encountered before.

Question 1.28

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After B cells are activated and divide into many plasma cells, some of these plasma cells become long-lived memory cells, capable of recognizing that same antigen if the pathogen should ever infect the organism again. T cells are also capable of becoming memory cells that will activate in the event that the same pathogen infects the body again, although these cells do not produce antibodies.

Describe the process that leads to the production of pathogen-specific cytotoxic T cells and how these cells fight pathogens.

Question 1.29

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Cells that are displaying foreign antigens. These cells can be phagocytes that have engulfed pathogens.

Question 1.30

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Once a cytotoxic T cell recognizes a foreign antigen on an antigen-presenting cell (a phagocyte, for example), it is activated and divides to produce many cytotoxic T cells to fight the infection.

Question 1.31

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Cytotoxic T cells bind to and kill pathogens (or foreign cells) directly by secreting chemicals that make the cell self-destruct.

Question 1.32

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Some of the cytotoxic T cells that are activated and produced during the pathogen response become long-lived memory cytotoxic T cells that will be able to recognize and respond to that same pathogen if it invades again.

Explain the relationship between primary and secondary immune responses and vaccination.

Question 1.33

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The response of the adaptive immune system when it encounters a pathogen for the first time. This response is usually slow.

Question 1.34

Yv15ONAnjbKx70UulX+hOpLbMXzr+9xqjGWGPZOd/c3zKouapWx7jN4Q6BKNcYc8ImTKLtkZB8Y=
The response of the adaptive immune system when it encounters a pathogen that it has seen and attacked before. This response is usually rapid and strong.

Question 1.35

8thK6e7SM9xBufrSPERpSa+ZzXaQHr0l4SIgqbDFjwOHTyBNPgnXNSeQrk70D8ZAlQOO4emaxT9CMVmBPLtGSPIMezrOnrX4Mfgxgg==
killed or weakened pathogens or parts (antigens) of pathogens

Question 1.36

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Vaccination is injection of the pathogen’s antigens or a killed or weakened pathogen. This causes a primary immune response, so B and T cells recognize the antigens of the pathogen and mount an immune response against the pathogen. Since the pathogen is killed or weakened, however, it is incapable of causing actual disease or illness, although some people may have an allergic reaction to proteins in the vaccine. So the primary immune response develops without the actual disease.

Question 1.37

jisDWzExtLHyBYtcbzVTpiC/tTxLe0LDl/5Pg8AidBsYt5ryFRPo2A3tuU+TQbv5J/cGeePEXz9FgUAQHdfyJQ==
Vaccination essentially produces a primary immune response to the pathogen. One thing that comes out of that primary immune response is memory cells (both B and T). In case of another encounter with that particular pathogen, the memory B and T cells will recognize the pathogen and mount an swift and effective response to eliminate it (a secondary response). This secondary response is so effective that the pathogen does not have time to infect and cause disease, so no signs or symptoms of disease develop.

Review Questions

Question 1.38

1Io/0wl+yKESaHBA3ZCzHhhYVEJVH8C8/f9MgCYz/IuAXlvfuhrS+Ys568TzXuGNu4oSZFMerYV1HI781qq0bGuntW99SKDwvmX3jQJf3myt1eK2voqO8s9Y6/o1X6Y4nFv3yO1KLGQ5YutR72+Q86Cz0UZF3NFbc6EegzCnP0NwBG7XpnIrbB9ZwWlglo7UjxkBievnU+fFskmIuXtJ1ueGBZOeCEYV
2
Try again.
Correct.
Incorrect.

Question 1.39

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Correct.
Incorrect.

Question 1.40

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Correct.
Incorrect.

Question 1.41

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2
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Correct.
Incorrect.

1.5 Driving Question 4:

Driving Question 4

What specific features of influenza virus allow it to cause worldwide outbreaks?

Why should you care?

You and/or your parents may remember the influenza pandemics of 1968 (the Hong Kong flu); you certainly should remember the H1N1 (swine flu) pandemic that began in 2009. Neither of these events was as severe as the Spanish influenza pandemic of 1918, but they serve as important reminders that influenza pandemics are unavoidable. That’s because influenza viruses change, both gradually via mutation and rapidly via gene swapping. Influenza researchers say that the question is not whether a new pandemic of severe influenza will occur, but when.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Compare and contrast the processes of antigenic drift and antigenic shift.
  2. Explain why antigenic shift is more likely to lead to new influenza pandemics than antigenic drift.
  3. Explain why public health officials monitor the types of influenza viruses infecting nonhuman animals as part of their surveillance against potentially human pandemic influenza strains.

Infographic Focus

The Infographics most pertinent to the Driving Question are 31.5 and 31.10, and Table 31.1.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
5o6TL0NZPYxqz37b/xuIHIqcm9N3q1Znr37VikIKJUcBsTQcHWSWyQ== Changes in antigens that occur when viruses exchange genetic material with other strains.
L5pAZitfoHtDGKlBymWkk14rzgZxD0rpju6prNHlUuw0AYd5COoVWg== Changes in viral antigens caused by genetic mutation during normal viral replication.
Table
2
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Correct.
Incorrect.

Compare and contrast the processes of antigenic drift and antigenic shift.

Question 1.42

Complete the table to compare and contrast antigenic drift and antigenic shift.

Do genetic changes happen quickly or slowly? How do genetic changes occur? Are genetic changes relatively small or relatively large? Change in Surface Antigens
Antigen drift WYCxiN3Q6tJCdU6I WYCxiN3Q6tJCdU6I WYCxiN3Q6tJCdU6I WYCxiN3Q6tJCdU6I
Antigen shift WYCxiN3Q6tJCdU6I WYCxiN3Q6tJCdU6I WYCxiN3Q6tJCdU6I WYCxiN3Q6tJCdU6I
Table
Do genetic changes happen quickly or slowly? How do genetic changes occur? Are genetic changes relatively small or relatively large? Change in Surface Antigens
Antigen drift Slowly Through point mutations Small Slight
Antigen shift Quickly Through whole gene exchange Large Drastic
Table

Question 1.43

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Antigen drift and shift both result in altered genomes, and thus altered antigens, of the virus. Antigen drift happens slowly, point mutation by point mutation, and does not involve genes from other strains of virus, so it results in only slightly different viral antigens. Antigen shift, however, happens rapidly because two strains of virus exchange genetic information to produce a new hybrid virus with a genome made from both viruses, resulting in drastically different viral antigens.

Explain why antigenic shift is more likely to lead to new influenza pandemics than antigenic drift.

Question 1.44

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Antigen shift is more likely to lead to a new influenza pandemic because virus mutation is rapid and extreme. New genomes, and thus completely new antigens, can be made between influenza from pigs and birds and humans, which the human immune system has never seen. There would be no immune memory in this case, so the likelihood of disease is great.

Explain why public health officials monitor the types of influenza viruses infecting nonhuman animals as part of their surveillance against potentially human pandemic influenza strains.

Question 1.45

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Pig and bird influenza viruses are capable of undergoing antigenic shift with human influenza viruses. This means that antigens from pigs or birds, which have never been seen by the human immune system, can become incorporated into a human influenza virus. This has the potential to produce a virus that can infect humans at a high rate and cause devastating disease.

Review Questions

Question 1.46

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Correct.
Incorrect.

Question 1.47

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Correct.
Incorrect.

Question 1.48

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2
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Correct.
Incorrect.