Surface projection of murine major histocompatibility determinants induced by hydrostatic pressure and cytokines.

Augmentation of surface presentation of the major histocompatibility complex (MHC) is a leading trend for preparation of tumor vaccines. Exposure of weakly immunogenic tumor cells, such as murine B16 melanoma, to hydrostatic pressure (P) in the presence of the membrane-impermeable protein crosslinker (CL) 2',3'-adenosine dialdehyde, was previously shown to induce a substantial increase in surface presentation of MHC molecules. When B-16 melanoma cells, used here as a model, were first treated for 72 h with interferon-gamma or tumor necrosis factor-alpha at concentrations of 10 and 100 units/ml, respectively, followed by application of pressure and cross-linking (PCL), the surface presentation of H2b molecules increased by 40% compared to treatment with cytokines alone, and by up to 1,700% when compared to treatment with PCL alone. Neither P nor CL alone enhanced the MHC presentation when cells were pretreated with these cytokines. The changes in MHC observed after the cytokine treatment were transient and decayed within several hours. However, the changes induced by the sequential treatment with cytokines and PCL were sustained for at least 96 h post-PCL which is of prime importance for immunogenic expression. A series of analogous experiments in the presence of cycloheximide indicated that approximately 50% of the observed PCL-induced increase in MHC projection originates from protein synthesis while the other 50% corresponds to passive translocation of MHC compartments. B16 melanoma cells, modified by the sequential treatment of cytokines and PCL, proved to be substantially more immunogenic by an in vitro sensitization assay than cells treated by either one of these treatments alone. These results may provide a guideline for the preparation of tumor vaccines which could be applied in immunotherapy treatment of cancer.