Which of the following bacteria are individuals with complement deficiencies more susceptible to?

Correct Answer: B

Rationale: Individuals with complement deficiencies are more susceptible to encapsulated bacteria. Haemophilus influenzae is an encapsulated bacterium, making it the correct choice. The complement system plays a crucial role in opsonization and killing of encapsulated bacteria. Escherichia coli (choice A) is not an encapsulated bacterium, so complement deficiency doesn't significantly increase susceptibility. Staphylococcus aureus (choice C) and Mycobacterium tuberculosis (choice D) are also not encapsulated bacteria, therefore complement deficiencies do not have a direct impact on susceptibility to these pathogens.

Correct Answer: C

Rationale: The correct answer is C: Inducing inflammation and recruiting immune cells. Anaphylotoxins, such as C3a, C4a, and C5a, are small molecules that are released during complement activation. They play a crucial role in enhancing inflammation by attracting immune cells to the site of infection or injury. 1. Anaphylotoxins induce inflammation by stimulating the release of histamine and other inflammatory mediators. 2. They promote vasodilation and increase vascular permeability, allowing immune cells to easily reach the affected area. 3. Anaphylotoxins also act as chemoattractants, recruiting neutrophils, macrophages, and other immune cells to the site of inflammation to help fight against pathogens. 4. These molecules do not suppress inflammation (choice A), facilitate antigen presentation (choice B), or neutralize pathogens (choice D). Their primary function is to amplify the immune response by inducing inflammation and recruiting immune cells to combat infections

Correct Answer: B

Rationale: The correct answer is B: Cytotoxic T cells. Cytotoxic T cells are responsible for directly killing infected or foreign cells by releasing toxic substances that induce apoptosis in the target cells. This process helps eliminate the threats to the body. Helper T cells (Choice A) assist in coordinating immune responses but do not directly kill cells. Regulatory T cells (Choice C) play a role in suppressing immune responses to prevent autoimmunity but do not kill infected cells. Memory T cells (Choice D) are primed for rapid response upon re-exposure to a specific antigen but do not directly kill cells. Therefore, the correct choice is B as cytotoxic T cells are specifically designed for cell killing.

Correct Answer: B

Rationale: The correct answer is B: Affinity maturation. During a secondary immune response, B cells undergo somatic hypermutation, leading to the production of antibodies with higher affinity for the antigen. This process occurs in germinal centers within secondary lymphoid organs. Isotype switching (A) refers to the change in antibody class but not affinity. Somatic recombination (C) is the process of creating diverse antibody repertoires. Clonal expansion (D) involves the proliferation of antigen-specific B cells but does not directly address affinity enhancement.

Correct Answer: B

Rationale: The correct answer is B: Helper T cells. Helper T cells play a crucial role in activating B cells by releasing cytokines that stimulate B cell proliferation and differentiation into plasma cells, which produce antibodies. Cytotoxic T cells (A) are involved in directly killing infected cells. Regulatory T cells (C) suppress immune responses. Memory T cells (D) are responsible for maintaining immunological memory for future responses. Thus, Helper T cells are the key cell type that helps activate B cells.