HLA-B and viral infectious disease: These “variant, abacavir-dependent” tetramers, as well as wild-type K9F, HLA-B*57:01 tetramers generated in the absence of abacavir, were prepared with different fluorochromes allowing us to use the different tetramers in combinations to probe the abacavir-dependent cross-reactivities of the wild type yellow fever specific CD8+ T-cell response.