Who is credited with the discovery of phagocytosis?

Correct Answer: C

Rationale: The correct answer is C: Elie Metchnikoff. He is credited with the discovery of phagocytosis, the process in which certain cells engulf and digest foreign particles. Metchnikoff's research in the late 19th century laid the foundation for our understanding of the immune system. A: Edward Jenner is known for developing the smallpox vaccine. B: Louis Pasteur is famous for his work on germ theory and pasteurization. D: Paul Ehrlich is known for his contributions to immunology, such as developing the concept of antibodies and chemotherapy.

Correct Answer: B

Rationale: The correct answer is B: Plasma cells (derived from B lymphocytes). B lymphocytes are responsible for producing antibodies. When activated, B cells differentiate into plasma cells, which are specialized in secreting antibodies. Neutrophils are primarily involved in phagocytosis, not antibody production. Natural killer cells are involved in killing infected cells, not antibody production. Macrophages are phagocytic cells that present antigens to activate B lymphocytes but do not produce antibodies themselves. Therefore, the correct answer is B as plasma cells derived from B lymphocytes are primarily responsible for antibody production.

Correct Answer: B

Rationale: The correct answer is B: It is a dynamic field, continually evolving through research. Immunology is constantly evolving due to new discoveries and advancements in technology. Research in immunology leads to a deeper understanding of the immune system and its interactions with pathogens, cancer, and other diseases. This ongoing evolution is essential for the development of new treatments and vaccines. Explanation of why other choices are incorrect: A: It is largely static, with few modern discoveries - This is incorrect as immunology is a rapidly advancing field with numerous breakthroughs and discoveries. C: It exclusively studies pathogen biology - This is incorrect as immunology also encompasses the study of the immune system's responses to various stimuli, not just pathogens. D: It focuses solely on innate immunity - This is incorrect as immunology covers both innate and adaptive immunity, as well as the interactions between them.

Correct Answer: B

Rationale: The correct answer is B: Classical pathway. This pathway is activated by immune complexes containing IgG or IgM. When these antibodies bind to antigens, they trigger the classical pathway by forming a complex that activates C1q, initiating a cascade of reactions leading to inflammation and opsonization. The alternative pathway (A) is activated by microbial surfaces, while the lectin pathway (C) is activated by mannose-binding lectin binding to carbohydrates on pathogens. The terminal pathway (D) involves the formation of the membrane attack complex.

Correct Answer: D

Rationale: The correct answer is D, MHC molecules. PAMPs are conserved molecules found on pathogens that can trigger an immune response. MHC molecules are not PAMPs; they are part of the host's immune system used to present antigens to T cells. LPS, peptidoglycan, and viral RNA are examples of PAMPs as they are specific molecules found on pathogens that can be recognized by pattern recognition receptors on immune cells to initiate an immune response.