What is a defining characteristic of immunology as a scientific field?

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: 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.

Correct Answer: B

Rationale: The correct answer is B: Recognition of PAMPs via PRRs. Innate immunity distinguishes self from non-self by recognizing Pathogen-Associated Molecular Patterns (PAMPs) via Pattern Recognition Receptors (PRRs). This recognition triggers an immediate response to eliminate potential threats. Choices A, C, and D are incorrect because somatic recombination is a process in adaptive immunity, MHC molecules present antigens for recognition by T cells in adaptive immunity, and antibody production is part of adaptive immunity involving B cells.

Correct Answer: B

Rationale: The correct answer is B because NK cells do not require prior antigen sensitization to recognize and attack infected cells. This distinguishes them from other lymphocytes, such as T and B cells, which are part of adaptive immunity and require prior exposure to specific antigens. NK cells are part of innate immunity and can directly recognize and kill infected or abnormal cells without prior activation. Choices A, C, and D are incorrect as NK cells are not part of adaptive immunity, do not directly produce antibodies, and do not phagocytose pathogens.

Correct Answer: B

Rationale: The correct answer is B: Dendritic cells. Dendritic cells are antigen-presenting cells that bridge the innate and adaptive immune responses by capturing and presenting antigens to T cells, thus initiating the adaptive immune response. They are crucial for activating T cells and initiating specific immune responses. A: B cells are responsible for antibody production in the adaptive immune response, not for linking innate and adaptive immunity. C: Eosinophils are primarily involved in parasitic infections and allergic reactions, not in linking innate and adaptive immunity. D: NK cells are part of the innate immune system and are involved in detecting and killing infected cells, but they do not directly link innate and adaptive immunity.