What is the main limitation of innate immunity compared to adaptive immunity?

Correct Answer: B

Rationale: The main limitation of innate immunity compared to adaptive immunity is that innate immunity lacks memory and specificity. This means that innate immune responses do not improve upon repeated exposure to the same pathogen and cannot target specific antigens efficiently. Adaptive immunity, on the other hand, can remember previous encounters with pathogens and mount targeted responses. Choices A, C, and D are incorrect because innate immunity can produce cytokines, includes physical barriers like skin and mucous membranes, and can activate complement as part of its defense mechanisms.

Correct Answer: B

Rationale: The primary characteristic of a secondary immune response is that it is faster, stronger, and more specific. This is because memory cells generated during the primary response allow for a quicker and more efficient recognition and response to the same antigen upon re-exposure. This results in a faster production of antibodies, a stronger immune response, and increased specificity. Choice A is incorrect as secondary responses are actually faster and more specific. Choice C is incorrect as secondary responses can produce IgG antibodies in addition to IgM. Choice D is incorrect because memory cells are essential for secondary immune responses.

Correct Answer: C

Rationale: The correct answer is C, displaying antigen fragments for T cell recognition. MHC molecules bind to antigen fragments and present them on the cell surface for T cells to recognize. This process is crucial for activating the immune response. Choice A is incorrect as MHC molecules do not secrete cytokines. Choice B is incorrect as MHC molecules do not directly destroy pathogens. Choice D is incorrect as MHC molecules do not produce antibodies; that is the function of B cells.

Correct Answer: B

Rationale: The correct answer is B: Plasma cells. Plasma cells are a type of white blood cell that produces antibodies in response to antigens. They are essential in the immune response to help fight off infections and other diseases. Helper T cells (A) assist other immune cells but do not directly produce antibodies. Cytotoxic T cells (C) are responsible for killing infected cells, not producing antibodies. Regulatory T cells (D) help regulate the immune response but do not produce antibodies. In summary, only plasma cells are specifically designed to produce antibodies in the immune system.

Correct Answer: B

Rationale: The correct answer is B (IgG and IgM) because in Type II hypersensitivity, antibodies target antigens on cell surfaces or tissues. IgG and IgM antibodies are involved in this type of immune response by binding to antigens and triggering cell destruction through complement activation or phagocytosis. IgE and IgA (choice A) are typically associated with Type I and Type III hypersensitivity, respectively. IgD (choice C) is primarily involved in B cell activation, while IgA (choice D) is more commonly associated with mucosal immunity.