TAPBP and neuroblastoma: We tested the effects of WT tapasin, tapasin-TM, and tapasin-TN6-TM [the TN6 mutant cannot chaperone HLA-I molecules in vitro (20)], on expression levels of folded surface HLA-I molecules in seven neuroblastoma cell lines with varying degrees of baseline HLA-I expression by staining with the pan-allelic antibody W6/32.