CD4 and infection: They found a very similar trend of presentation of longer HLA-I peptides on HLA-B*40:01 and HLA-B*27:05 in CD4+ T cells upon activation or infection, that is HLA allotype dependent (49), where a more marked length shift was observed for HLA alleles that can accommodate longer peptides, and it was far less noticeable or not observed for more “rigid” HLA alleles, such as HLA-A*02:01.