Identify the function of perforins.

ATI RN

ATI RN Test Bank

A. Activate complement B. Bind to antigens C. Drills holes into plasma membranes D. Stimulate inflammation

Correct Answer: C

Rationale: Perforins from cytotoxic T cells drill holes in target membranes.

An example of secondary mediators released by Mast cells would be

A. histamine B. platelet activating factor C. heparin D. chymase

Correct Answer: B

Rationale: PAF is a secondary mediator; histamine , heparin , and chymase are primary.

Lysis of cells by complement is finalized by the formation of:

A. C1q B. Immune Complexes C. Membrane Attack Complex D. Properdin

Correct Answer: C

Rationale: Membrane Attack Complex lyses cells; C1q starts classical, immune complexes trigger, and properdin stabilizes alternative.

In activated T cells, CD152 (CTLA4) is expressed on the cell surface and inhibits the binding of CD28 on these same T cells to:

A. IL-2 B. CD4 C. CD8 D. CD80/86

Correct Answer: D

Rationale: CTLA4 blocks CD28-B7 (CD80/86); not IL-2 , CD4 , CD8 , or CD95 .

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