Question
Interferon gamma, which is known to enhance the cytotoxic effects of macrophages are secreted by which of the following components of the immune system?
| A. |
CD4 T cell
|
| B. |
CD8 + T cells
|
| C. |
RBC
|
| D. |
Neutrophils
|
Show Answer
|
Correct Answer » A
Explanation
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|
Interferon-gamma (IFN-γ) is the most important macrophage-activating cytokine.
Its major functions include:
- Activation of macrophages
- Enhancement of intracellular killing of microbes
- Promotion of antigen presentation (↑ MHC expression)
- Stimulation of cell-mediated immunity
- Promotion of Th1 immune responses
The principal source of IFN-γ is CD4⁺ T helper 1 (Th1) cells
Other cells that can produce IFN-γ include:
- Natural Killer (NK) cells
- CD8⁺ T cells
However, among the given options, CD4⁺ Th1 cells are the best answer.
Option Analysis
A. CD4⁺ T cell
More specifically:
- Th1 subset of CD4⁺ T cells
- Secretes:
Functions:
- Macrophage activation
- Defense against intracellular organisms (e.g., Mycobacterium tuberculosis)
B. CD8⁺ T cells
CD8⁺ cytotoxic T cells can produce IFN-γ, but they are primarily involved in:
- Killing virus-infected cells
- Tumor cell destruction
The principal source tested in immunology MCQs is Th1 CD4⁺ cells.
C. RBC
Red blood cells:
- Transport oxygen and carbon dioxide
- Do not participate in cytokine secretion
D. Neutrophils
Neutrophils are important phagocytes but are not a major source of IFN-γ.
They mainly:
- Phagocytose bacteria
- Release reactive oxygen species
- Form NETs (Neutrophil Extracellular Traps)
