HLA-B and melanoma: To examine whether HLA-B allotypes differ in their abilities to become expressed on the surface of TAP-deficient cells, several HLA-B allotypes that occur at the highest frequencies in United States populations were expressed in the TAP1-deficient human melanoma cell line SK-mel-19 (SK19) [37] or in a TAP2-deficient human fibroblast cell line STF1 [38] using the previously described retroviral infection method [22, 39].