Question

In a mixed lymphocyte reaction, T cells from individual A make a robust

response to antigen-presenting-cells from individual B, as long as the two individuals
express different alleles of MHC molecules. Estimates indicate that up to 10% of the T
cells from individual A may contribute to this response. If one performed this assay using
responder T cells from a child and antigen-presenting cells from one parent, the result
would be:

A. A massive proliferative response made by the antigen-presenting cells of the parent
B. A very weak response by the child's T cells, involving only 0.1% of their T cells
C. The complete absence of any proliferative response by the child's T cells
D. A robust cytolytic response that kills all of the parent's antigen-presenting cells
E. A robust response by the child's T cells

Answer 1

In a mixed lymphocyte reaction between a child's T cells and one parent's APCs, a very weak response by the child's T cells is expected due to shared MHC molecules. The child will likely recognize many of the parent's MHC as self, leading to little to no response. OPTION B IS ANSWER

Step-by-step explanation:

The mixed lymphocyte reaction (MLR) involves two main types of cells: T cells and antigen-presenting cells (APCs). In an MLR assay, T cells from one individual are exposed to APCs from another individual. If the two individuals express different alleles of MHC molecules

The T cells can have a robust response because they recognize the foreign MHC molecules as non-self. However, in the instance where responder T cells from a child and antigen-presenting cells from one parent are used, one would not expect a massive response for a couple of reasons:

• The child inherits MHC alleles from both the mother and the father, thus some of the child's T cells will recognize the parent's MHC molecules as 'self' and not mount a strong response.
• A child's T cells might recognize some of the parent's MHC molecules as non-self if they are inherited from the other parent, but this will comprise only a subset of the child's T cell repertoire.

Considering the principles of clonal selection and clonal expansion, the most likely outcome of this reaction would be a very weak response by the child's T cells, involving only a small percentage of their T cells. This is due to the fact that most of the child's T cells should recognize the parent's MHC molecules as self, reducing the potential for a robust response. OPTION B IS ANSWER