Which antibody dominates the primary immune response?

Correct Answer: C

Rationale: The correct answer is C: IgM. During the primary immune response, IgM is the first antibody produced by the immune system in response to an antigen. IgM is efficient in agglutination and complement fixation, aiding in the elimination of pathogens. IgG is more prominent in the secondary immune response. IgA is mainly found in mucosal areas. IgE is associated with allergic reactions and parasitic infections, not the primary immune response. So, IgM dominates the primary immune response by being the initial antibody produced to combat antigens.

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.

Correct Answer: B

Rationale: The correct answer is B: Thyroid-stimulating hormone (TSH) receptor. In Grave's disease, autoantibodies bind to and activate the TSH receptor on thyroid cells, leading to hyperthyroidism. This is a Type II hypersensitivity reaction. Insulin receptor (A) is not involved in Grave's disease. Complement receptor (C) is not the target in this condition. CD4 receptor (D) is primarily involved in T cell activation, not in Grave's disease.