Which of the following statements is true about T regulatory cells

Correct Answer: A

Rationale: Rationale: A. T regulatory cells can produce TGF-β, which is a key immunosuppressive cytokine regulating immune responses. B. T regulatory cells do not express AIRE, a transcription factor mainly involved in central tolerance. C. T regulatory cells can control both TH1 and TH2 responses, maintaining immune homeostasis. D. T regulatory cells do not act by killing other T cell subsets, but rather through suppressive cytokines and cell-cell interactions.

Correct Answer: C

Rationale: The correct answer is C: Natural killer cells. Natural killer cells are part of the innate immune system and play a crucial role in identifying and destroying infected or abnormal cells. They are able to recognize and target cells that lack specific markers, providing a rapid response to infections. Explanation for incorrect choices: A: B lymphocytes are part of the adaptive immune system, not innate immunity. B: T lymphocytes are also part of the adaptive immune system, not involved in innate immunity. D: Plasma cells are differentiated B cells that produce antibodies in the adaptive immune response, not part of innate immunity.

Correct Answer: C

Rationale: The correct answer is C: IFN-alpha. This is because IFN-alpha belongs to the interferon family, not the interleukin family. Interleukins are a subset of cytokines that are primarily involved in regulating immune responses, while interferons have antiviral properties. IL-1, IL-22, and IL-10 are all interleukins and are part of the interleukin family. Therefore, IFN-alpha is the only cytokine listed that is not included in the interleukin family.

Correct Answer: B

Rationale: The correct answer is B: Fighting cancer by targeting abnormal cells. The immune system plays a crucial role in cancer by identifying and eliminating abnormal cells that can develop into tumors. This process is known as immunosurveillance. Through mechanisms like T cells and natural killer cells, the immune system can detect and destroy cancerous cells before they can grow and spread. This function is essential in preventing the development and progression of cancer. Choices A, C, and D are incorrect: A: Promoting cell growth - The immune system does not promote cell growth in cancer; rather, it regulates and suppresses the growth of abnormal cells. C: Enhancing pathogen resistance - While the immune system does enhance resistance against pathogens, this is not its critical function in cancer. D: Stimulating autoimmune responses - Autoimmune responses involve the immune system attacking healthy cells, not targeting cancerous cells.

Correct Answer: A

Rationale: Louis Pasteur is credited with introducing the germ theory of disease. He conducted experiments that demonstrated the role of microorganisms in causing infections. He also developed pasteurization to kill harmful bacteria in food and beverages. Edward Jenner is known for developing the smallpox vaccine, not the germ theory. Elie Metchnikoff studied the immune system and phagocytosis. Paul Ehrlich is known for his work on chemotherapy and the concept of the "magic bullet," targeting specific pathogens.