The molecule indicated on this illustration of the first signal during the activation of a cytotoxic T cell (T_C) must be

Question

The molecule indicated on this illustration of the first signal during the activation of a cytotoxic T cell (T_C)must be

Quizplus · Accepted Answer

The first signal during the activation of a cytotoxic T cell involves the binding of the T cell receptor (TCR) to an antigenic peptide presented by class I MHC molecules on the surface of the target cell. Therefore, the molecule indicated on this illustration must be class I MHC, which is recognized by CD8 molecules on the surface of the cytotoxic T cell. B and D are incorrect because class II MHC and B7 proteins are involved in the second signal, which is provided by antigen-presenting cells. C is incorrect because CD8 molecules are not present on the target cell, but rather on the surface of the cytotoxic T cell.

The Molecule Indicated on This Illustration of the First Signal