SURFACE PROJECTION OF MURINE MAJOR HISTOCOMPATIBILITY DETERMINANTS INDUCED BY HYDROSTATIC-PRESSURE AND CYTOKINES

Augmentation of surface presentation of the major histocompatibility c omplex (MHC) is a leading trend for preparation of tumor vaccines. Exp osure of weakly immunogenic tumor cells, such as murine B16 melanoma, to hydrostatic pressure (P) in the presence of the membrane-impermeabl e 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 ap plication of pressure and cross-linking (PCL), the surface presentatio n of H2(b) molecules increased by 40% compared to treatment with cytok ines alone, and by up to 1,700% when compared to treatment with PCL al one. Neither P nor CL alone enhanced the MHC presentation when cells w ere pretreated with these cytokines. The changes in MHC observed after the cytokine treatment were transient and decayed within several. hou rs. However, the changes induced by the sequential treatment with cyto kines and PCL were sustained for at least 96 h post-PCL which is of pr ime importance for immunogenic expression. A series of analogous exper iments in the presence of cycloheximide indicated that approximately 5 0% of the observed PCL-induced increase in MHC projection originates f rom protein synthesis while the other 50% corresponds to passive trans location of MHC compartments. B16 melanoma cells, modified by the sequ ential 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 guid eline for the preparation of tumor vaccines which could be applied in immunotherapy treatment of cancer.