Which of the following is NOT true. Passive immunization:

Correct Answer: D

Rationale: Passive immunization does not involve transferring naïve lymphocytes; instead, it transfers pre-formed antibodies for immediate protection. Choice D is incorrect because lymphocytes do not produce antibodies directly. Choices A, B, and C are correct: Passive immunization has been used for Ebola, transfers serum with antibodies, and provides immediate protection with pre-formed antibodies.

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.

Correct Answer: B

Rationale: Macrophages differentiate in tissues because they originate from monocytes which leave the bloodstream and mature into macrophages in various tissues. This process is essential for their diverse functions in immune response and tissue maintenance. Choices A, C, and D are incorrect because macrophages do not differentiate from blood neutrophils, the common lymphoid progenitor, or in the bone marrow.