Human immune response to DNP-modified autologous cells after treatment with a DNP-conjugated melanoma vaccine.

Immunizing patients with metastatic melanoma by injection of autologous tumor cells modified by DNP induces inflammatory responses in metastatic masses, which is sometimes associated with tumor regression. To elucidate this phenomenon, we studied the immune response to DNP-modified cells in these patients. All developed DTH to DNP-modified autologous lymphocytes (mean +/- SE: 13.3 +/- 1.3 mm), but not to TNP-modified lymphocytes. Larger responses (21.9 +/- 3.6 mm) were elicited by DNP-modified autologous melanoma cells. In 8/11 patients tested, PBL proliferated in vitro when stimulated by autologous DNP-modified lymphocytes, and in 5 patients the stimulation resulted in production of interferon-gamma. DNP-modified autologous melanoma cells elicited lymphocyte responses as well. PBL from 1 patient were expanded by culture in IL2 and repeated restimulation with DNP-modified B lymphoblastoid cells. This T cell line proliferated and produced interferon-gamma but not IL4, when stimulated by autologous DNP-modified lymphocytes or melanoma cells. Both CD4+ and CD8+ subpopulations responded as determined by panning experiments and by testing of phenotypically homogeneous cultures obtained by limiting dilution. Studies of a stable CD8+ subline of the expanded T cells indicated that the response to DNP-modified cells was MHC-restricted, since it was blocked by antibody to class I determinants. Moreover, these T cells were able to respond to allogeneic DNP-modified stimulators that were matched at one or both HLA-A loci, but not to stimulators that were HLA-A mismatched. Finally, the CD8+ subline killed DNP-modified autologous melanoma cells, but not an HLA-A mismatched allogeneic melanoma, in a 6-hr 51Cr-release assay. These results may have significant implications for understanding the pathogenesis of drug-induced autoimmunity and for the development of new approaches to cancer immunotherapy.