immuno q2 - jcbc

[ArchivalUser]

T cells that have a low affinity for MHC class I molecules differentiate in the thymus to become which type of cell?
A. CD 8 + cytotoxic lymphocyte
B. Gamma-delta T cell
C. Natural killer cell
D. T helper 1 cell
E. T helper 2 cell

[ArchivalUser]

A???

[ArchivalUser]

C. Natural Killer cell.

[ArchivalUser]

The correct answer is A. CD8+ cytotoxic T lymphocytes are positively selected in the thymus because they
have low affinity for MHC class I molecules. If they had possessed high affinity for the MHC class I molecules,
they would have been eliminated (negative selection) because of the danger of autoimmune disease. Also,
cells with no affinity for MHC class I molecules would be eliminated.
The gamma-delta designation in a T cell (choice B) refers to type of receptor on the cell. Most T-cell receptors
are alpha-beta receptors, but some are of a different isotype termed gamma-delta.
Natural killer cells (choice C) are large granular lymphocytes that are part of the innate immune response.
Natural killer cell function does not depend on MHC class I or class II molecules; it simply kills tumor cells or
virally infected cells.
T helper 1 (choice D) and T helper 2 cells (choice E) would have a low affinity for class II MHC molecules in
order to survive in