Which of the following is not an outcome of phagocytosis in macrophages

Correct Answer: D

Rationale: The correct answer is D: Complement activation. Phagocytosis by macrophages involves engulfing and digesting pathogens. Complement activation occurs through a separate pathway involving a series of proteins that enhance the immune response. Phagocytosis does not directly lead to complement activation. Choices A, B, and C are outcomes of phagocytosis in macrophages: Respiratory burst involves production of reactive oxygen species, nitric oxide production helps destroy pathogens, and antigen presentation is important for activating other immune cells.

Correct Answer: D

Rationale: The Fc regions of antibodies interact with various immune cells and molecules to mediate effector functions. - A: Degranulation of mast cells: Fc receptors on mast cells bind to antibody Fc regions, triggering degranulation. - B: ADCC: Fc regions bind to Fc receptors on immune cells, facilitating target cell killing. - C: Complement activation: Antibody binding to antigens can activate the complement system via the Fc region. Therefore, the correct answer is D because the Fc regions of antibodies are involved in all mentioned effector functions.

Correct Answer: C

Rationale: The correct answer is C: Secondary lymphoid tissues. Naïve T cells are activated in secondary lymphoid tissues such as lymph nodes and spleen. These tissues are where T cells encounter antigen-presenting cells, receive co-stimulatory signals, and undergo clonal expansion to differentiate into effector T cells. Germinal centers are primarily for B cell responses. Primary lymphoid tissues (bone marrow and thymus) are where T cells mature but not where activation occurs. Choice D is incorrect as naïve T cell activation does occur in secondary lymphoid tissues.

Correct Answer: A

Rationale: The correct answer is A: Louis Pasteur. He is considered to have created the first "attenuated" vaccine based on his work with the rabies vaccine in the 1880s. Pasteur's method involved weakening the virus to make it less harmful while still eliciting an immune response. Other choices are incorrect because: B: Robert Koch is known for his contributions to microbiology and germ theory, not for creating the first attenuated vaccine. C: Ilya Metchnikoff is known for his work on immunology and phagocytosis, not for developing the first attenuated vaccine. D: Adolf Von Behring is known for his research on diphtheria antitoxin, not for creating the first attenuated vaccine.

Correct Answer: A

Rationale: The correct answer is A: It is the causal agent of "hamburger disease." Salmonella typhimurium is not the causal agent of "hamburger disease." Instead, Escherichia coli O157:H7 is the primary causal agent of this particular foodborne illness. Salmonella typhimurium is commonly associated with causing salmonellosis. Therefore, choice A is incorrect. Choices B, C, and D are all true statements about Salmonella typhimurium. It is the second most common cause of food poisoning, it is able to induce its own uptake by manipulating the actin cytoskeleton of host cells, and it is able to survive inside the phagosomes by manipulating the host actin cytoskeleton.