Which immune cells are primarily responsible for antibody production?

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: 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.

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.