Question

MHC class II molecules expressed on the surface of thymic cortical epithelial cells normally have a wide repertoire of different peptides bound to them. By engineering a construct that fuses the MHC class II protein to a single peptide sequence, and expressing this construct in thymic cortical epithelial cells that have their endogenous MHC class II genes knocked out, it is possible to generate a mouse line where all MHC class II proteins expressed on all thymic cortical epithelial cells are bound to the same peptide. These mice are often referred to as ‘single-peptide’ mice. Examination of the T cell developing in these single peptide mice would likely show:
A. A significant reduction in the numbers of mature CD4 T cells
B. No change in the numbers of mature CD4 T cells
C. A block in T cell development at the CD4+CD8+double-positive stage
D. A repertoire of T-cell receptors on mature CD4 T cells restricted to a single Vbeta
E. A block in T cell development at the CD4-CD8-double-negative stage

Answer 1

Answer:

A. A significant reduction in the numbers of mature CD4 T cells

Explanation:

In the given problem, there is an engineering of the MHC class II protein with the sequence of a single peptide. In addition, it was expressed in the epithelial cells of the thymic cortical. Based on the result obtained from the engineering construction, it is obvious that there would be a large decreases in the CD4 T cells numbers.