What is the typical outcome of a C1q deficiency in the complement system?

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Immune System Quizlet Questions

Question 1 of 5

What is the typical outcome of a C1q deficiency in the complement system?

Correct Answer: C

Rationale: The correct answer is C: Autoimmune diseases such as SLE. C1q is essential for the classical pathway of the complement system, which plays a crucial role in clearing immune complexes. A deficiency in C1q can lead to impaired immune complex clearance, resulting in the development of autoimmune diseases like Systemic Lupus Erythematosus (SLE). Choice A (Enhanced inflammation) is incorrect because a deficiency in C1q would actually lead to decreased inflammation due to impaired complement activation. Choice B (Reduced phagocytosis) is incorrect because phagocytosis is primarily mediated by the alternative pathway of the complement system, not the classical pathway involving C1q. Choice D (Increased cancer risk) is incorrect as C1q deficiency is not directly associated with an increased risk of cancer.

Question 2 of 5

Which antibody is transported across the placenta?

Correct Answer: C

Rationale: The correct answer is C: IgG. IgG is the only antibody that can be transported across the placenta from the mother to the fetus, providing passive immunity to the newborn. This transfer of IgG occurs through the neonatal Fc receptor (FcRn) present in the placenta. IgA is primarily found in mucosal secretions, IgM is too large to cross the placenta, and IgE is involved in allergic reactions and parasitic infections, not placental transfer. Therefore, IgG is the only antibody capable of crossing the placenta and providing immune protection to the fetus.

Question 3 of 5

What are the two main outcomes of clonal selection?

Correct Answer: B

Rationale: The correct answer is B: Differentiation into effector and memory cells. During clonal selection, activated lymphocytes undergo differentiation into effector cells that combat the current infection and memory cells that provide long-lasting immunity. Effector cells directly eliminate pathogens, while memory cells remember the specific pathogen for future encounters. Choices A, C, and D are incorrect as they do not accurately represent the main outcomes of clonal selection. T cell activation and cytokine suppression (A) are processes involved in immune response regulation rather than the direct outcomes of clonal selection. Pathogen destruction and tissue repair (C) are broader immune responses that occur after clonal selection. Phagocytosis and complement activation (D) involve innate immune responses, not the adaptive immune responses seen in clonal selection.

Question 4 of 5

What is the significance of isotype switching in B cells?

Correct Answer: C

Rationale: Isotype switching in B cells involves changing the constant region to produce different antibody isotypes, such as IgG, IgA, or IgE. This is important for diversifying the functions of antibodies without altering antigen specificity. It allows for different effector functions, such as opsonization, neutralization, or complement activation. This process does not eliminate antigen-specific B cells, as it maintains the immunological memory. Isotype switching does not directly affect antibody affinity for antigens, which is primarily determined by somatic hypermutation and affinity maturation. It is not limited to producing IgM only, as B cells can switch to other isotypes based on the cytokine microenvironment.

Question 5 of 5

What is a characteristic feature of atopy?

Correct Answer: A

Rationale: Step-by-step rationale: 1. Atopy is a genetic predisposition to produce IgE antibodies in response to allergens. 2. IgE antibodies play a crucial role in allergic reactions. 3. Individuals with atopy have an exaggerated immune response to allergens. 4. Excess production of IgA antibodies (B) and suppressed immune response to allergens (C) are not characteristic features of atopy. 5. Delayed hypersensitivity reactions (D) involve a different immune mechanism compared to the immediate IgE-mediated response in atopy.

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