Which cells are responsible for antigen presentation to T cells?

Correct Answer: B

Rationale: The correct answer is B: Antigen-presenting cells (APCs). APCs, such as dendritic cells, macrophages, and B cells, are specialized cells that capture, process, and present antigens to T cells to initiate an immune response. They express major histocompatibility complex (MHC) molecules for antigen presentation. Plasma cells (A) produce antibodies, NK cells (C) are involved in killing infected cells, and eosinophils (D) are primarily involved in parasitic infections and allergic responses, not antigen presentation to T cells.

Correct Answer: B

Rationale: The correct answer is B: Major Histocompatibility Complex (MHC). MHC molecules present antigens to T cells for immune response activation. They bind to antigenic peptides and present them on the cell surface for recognition by T cells. This is crucial for the immune system to distinguish between self and non-self antigens. Antibodies (A) are produced by B cells and do not directly present antigens to T cells. Complement protein C3 (C) is involved in the complement system for immune defense, not antigen presentation. Cytokines (D) are signaling molecules that regulate immune responses but do not directly present antigens to T cells.

Correct Answer: C

Rationale: The correct answer is C: Neutralization, opsonization, and complement activation. Antibodies play a crucial role in adaptive immunity by neutralizing pathogens, facilitating their destruction through opsonization, and activating the complement system for pathogen elimination. This is achieved through binding to antigens on pathogens, marking them for destruction by phagocytes, and triggering the complement cascade. Options A, B, and D are incorrect because antibodies do not directly present antigens, perform phagocytosis, or kill infected cells.

Correct Answer: B

Rationale: The correct answer is B: Immediate phase and late phase. In Type I hypersensitivity, the immediate phase occurs rapidly after exposure to an allergen, leading to the release of mediators like histamine. The late phase occurs several hours later, involving sustained inflammatory response. A: Early phase and latent phase - Incorrect because the terms do not accurately describe the phases of Type I hypersensitivity. C: Acute phase and chronic phase - Incorrect because Type I hypersensitivity does not typically progress to a chronic phase. D: Primary phase and secondary phase - Incorrect as these terms are not commonly used to describe the phases of Type I hypersensitivity.

Correct Answer: B

Rationale: The correct answer is B: A collection of macrophages filled with antigens. Granulomas are tissue responses to chronic inflammation, where macrophages form a cluster to engulf and contain foreign substances like antigens. This leads to the formation of a granuloma, which can be seen in conditions like tuberculosis. Other choices are incorrect because: A) Antibodies are proteins produced by the immune system, not structures like granulomas; C) Mast cells are involved in allergic reactions and not typically associated with granulomas; D) An antibody-antigen complex is a different concept related to immune response but not specific to granulomas.