Which cells are involved in innate immunity?

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: 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.

Correct Answer: B

Rationale: The correct answer is B - Macrophages and neutrophils are the most important phagocytes in innate immunity. Macrophages are versatile cells that engulf and destroy pathogens, while neutrophils are the most abundant phagocytes in the blood and are critical for early immune responses. Natural killer cells and B lymphocytes (A) are not phagocytes, but rather involved in adaptive immunity. T cells and dendritic cells (C) play roles in adaptive immunity and antigen presentation, not direct phagocytosis. Basophils and eosinophils (D) are involved in allergic reactions and parasitic infections, not primary phagocytic functions.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.