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+--- Thread: immuno q2 - jcbc (/showthread.php?tid=294945)
immuno q2 - jcbc - ArchivalUser - 04-21-2008
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
0 - ArchivalUser - 04-21-2008
A???
0 - ArchivalUser - 04-21-2008
C. Natural Killer cell.
0 - ArchivalUser - 04-21-2008
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