Cell-Mediated Immunity · Pathology

Which molecule provides a key costimulatory signal for T-cell activation?

  1. CD28 binding to B7
  2. CD8 binding to MHC II
  3. IgM binding to antigen
  4. Complement C5a
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Correct answer: CD28 binding to B7

T-cell activation requires costimulation, commonly through CD28 on T cells binding to B7 molecules on antigen-presenting cells. Without this signal, T cells may become anergic.

Difficulty: Medium Question 7 of 20

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