Ex Vivo Expansion of CD8+CD56+ and CD8+CD56- Natural Killer T Cells Specific for MUC1 Mucin
Abstract
Prostate cancers express MUC1, but nearly all metastatic cells lack HLA class I molecules. Thus, a lymphocyte population that can sense its antigenic environment, while also able to react to stimuli of natural killer (NK) cells, may be a more versatile effector cell population for antitumor immune responses. Herein, we report that tumor-specific MUC1 peptide, interleukin 2, and interleukin 12 act synergistically to stimulate the ex vivo expansion of CD8 + CD56 - T cells and CD8 + CD56 + natural killer T (NKT) cells from the peripheral blood mononuclear cells of prostate cancer patients, as well as healthy male and female donors. Both the CD56 + NKT cells and CD56 - T cells lysed allogeneic mucin-bearing target cells, as well as NK target cells, but not lymphokine-activated killer target cells. However, the CD56 + NKT cells displayed a 2-fold greater cytolytic activity than the CD56 - T cells. The mucin-specific cytolytic activity and NK cytolytic activities for both lymphocyte populations were independent of HLA class I and CD1 molecules. The CD56 - T cells up-regulated CD56 with continued antigenic stimulation in the presence of interleukin 12, suggesting that CD8 + CD56 - T cells are NKT cells. However, CD56 + NKT cells expand poorly to continued stimulation. All mucin-stimulated NKT cells exhibited the activated/memory CD45RO phenotype. The NKT cell lines express the /ß T-cell receptor (TCR). The TCR repertoire was limited and varied with cell line, but was not the V 24Vß11 TCR typically associated with NKT cells. Whereas CD161 is generally considered a marker of NKT cells, the mucin-stimulated NKT cells did not express this marker. Thus, we have described two phenotypically distinct NKT types that do not display a biased TCR repertoire, but do display specificity for a tumor-specific peptide antigen (CTL-like activity), as well as HLA class I-deficient target cells (NK-like activity).