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Section 13: Immunologic Disorders

Which of the following receptors does not inhibit T-cell activity?

A. PD-1

B. CD28

C. CTLA-4

D. Fas

The answer is B. PD-1, CTLA-4, and Fas receptors all send inhibitory signals to T-cells once they bind to their ligands. CD28 binds to CD80 or CD86 and is part of the signaling pathway that results in T-cell activation.

Which of the following is a part of the adaptive immune system?

A. Macrophage

B. Eosinophil

C. B cell

D. Neutrophil

The answer is C. Macrophages, eosinophils, and neutrophils are all components of the innate immune system. B cells are able to recognize new antigens and develop into memory cells that allow for a more rapid and potent immune response upon additional exposure to an antigen, hence their classification as a component of the adaptive immune system.

Which antibody type is usually produced when the immune system first encounters a pathogen?

A. IgA

B. IgD

C. IgG

D. IgM

The answer is D. Upon exposure to a given antigen, plasma cells secret IgM initially. Over time, plasma cells eventually switch over to the secretion of IgG.

Activation of the complement system can result in all of the following, except:

A. The stimulation of plasma cells to secrete antibodies

B. Opsonization of foreign pathogens

C. Lysis of microorganisms

D. Stimulation of chemotaxis of phagocytes

The answer is A. The complement system does not signal plasma cells to secrete antibodies. The complement system can opsonize foreign pathogens, preventing the pathogen from interacting with or infecting cells or structures in the body. Additionally, opsonization may signal granulocytes, such as neutrophils to phagocytose and destroy the pathogen. Additionally, the binding of complement has been shown to result in the lysis of certain microorganisms and cells. Finally, Breakdown products of complement (C3a and C5a) can serve as chemoattractants which help to draw neutrophils to infected tissues.

Which of the following treatments depends on passive immunity?

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