ANTIGEN-PROCESSING MUTANT T2 CELLS PRESENT VIRAL-ANTIGEN RESTRICTED THROUGH H-2KB

Cytotoxic T lymphocytes (CTL) recognize foreign antigens as short pept ides presented by class I molecules of the major histocompatibility co mplex (MHC). T2 cells are profoundly defective in the presentation of endogenously synthesized antigens to CTL due to a deletion of MHC clas s II-encoded genes for transporters associated with antigen presentati on (TAP1/TAP2). Surprisingly, we here demonstrate that T2 cells, after infection with Sendai virus, are readily killed by H-2K(b) restricted CD8+ T cells. In contrast to classical class I-mediated antigen prese ntation, the presentation of Sendai virus antigen in T2K(b) cells is b refeldin A (BFA) insensitive.The present findings may suggest the pres ence of an alternative pathway for MHC class I-mediated antigen presen tation in T2 cells.