A patient with an anti-HLA-A2 antibody would be most likely to have a positive T cell crossmatch with which of the following donors?

The presence of anti-HLA-A2 antibodies in a patient indicates that the immune system recognizes HLA-A2 as foreign, which can lead to an immune reaction if matched with a donor expressing this antigen. In the context of T cell crossmatching, a positive result typically occurs when a recipient’s antibodies react against donor lymphocytes that express the same HLA antigen that the patient is sensitized to, resulting in a complement fixation or cell lysis.

When considering the provided options, the correct choice demonstrates that none of the listed HLA alleles found in the donor profile express HLA-A2. The donor options where HLA-A2 is absent, hence they would carry a risk of a positive T cell crossmatch due to the presence of anti-HLA-A2 antibodies, must be identified.

In this case, option B lists HLA alleles A24 and A68 in addition to B7 and B64, none of which contains HLA-A2. Since the patient’s anti-HLA-A2 antibodies would specifically target cells that express the HLA-A2 antigen, choosing a donor who does not express HLA-A2 ensures that there is a potential for a positive crossmatch, as any other HLA-A2 alleles