Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

21. The Immune System

Antigens

Anatomy & Physiology

21. The Immune System

Antigens

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Problem 18

Textbook Question

A decrease in which population of lymphocytes would impair all aspects of an immune response?
(a) Cytotoxic T cells
(b) Helper T cells
(c) Regulatory T cells
(d) B cells
(e) Plasma cells

Verified step by step guidance

Understand the role of each lymphocyte type in the immune response: Cytotoxic T cells (a) destroy infected or abnormal cells, Helper T cells (b) coordinate the immune response by activating other immune cells, Regulatory T cells (c) suppress immune responses to prevent overactivity, B cells (d) produce antibodies, and Plasma cells (e) are the activated form of B cells that secrete antibodies.

Recognize that the question is asking about a lymphocyte population whose decrease would impair all aspects of the immune response, meaning it plays a central and coordinating role.

Recall that Helper T cells (b) are essential for activating both cytotoxic T cells and B cells, as well as enhancing the activity of other immune cells like macrophages. Without Helper T cells, the immune system's ability to respond to pathogens is severely compromised.

Eliminate the other options: Cytotoxic T cells (a) are important for killing infected cells but do not coordinate the entire immune response. Regulatory T cells (c) suppress immune activity but are not central to initiating it. B cells (d) and Plasma cells (e) are involved in antibody production but rely on Helper T cells for activation.

Conclude that the correct answer is Helper T cells (b), as their decrease would impair all aspects of the immune response due to their central role in immune coordination.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Helper T Cells

Helper T cells, or CD4+ T cells, play a crucial role in the immune response by activating and regulating other immune cells, including B cells and cytotoxic T cells. They are essential for orchestrating the adaptive immune response, and a decrease in their population can lead to a weakened immune system, making it difficult for the body to respond effectively to infections.

Cytotoxic T Cells

Cytotoxic T cells, or CD8+ T cells, are responsible for directly killing infected or cancerous cells. They recognize antigens presented by infected cells and initiate apoptosis. While important for targeting infected cells, their function is heavily reliant on the activation signals provided by helper T cells, indicating that a decrease in helper T cells would also impair cytotoxic T cell activity.

B Cells

B cells are a type of lymphocyte that produce antibodies in response to antigens. They are crucial for humoral immunity, which is the aspect of the immune response that involves the production of antibodies to neutralize pathogens. Helper T cells are vital for B cell activation and differentiation, meaning that a decrease in helper T cells would significantly impair B cell function and the overall immune response.

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