In vitro analysis of the mode of action of the immuno-suppressive drug 15-deoxyspergualin.

The purpose of the study was to analyse the action of the immunosuppressive drug 15-deoxyspergualin (DOS) in vitro. We studied: a) the influence of DOS alone and DOS in combination with various monoclonal antibodies on alloantigen stimulation in the mixed lymphocyte culture (MLC), b) the influence of DOS treatment on the MHC class I and II expression of splenocytes, lymph node cells and peritoneal macrophages, c) the influence of DOS treatment on a suppressor cell population. Our study showed that: a) DOS inhibits interleukin 1 (IL-1) secretion by macrophages, leading to reduction of immune response to alloantigens. This effect was neutralized by addition of IL-1; b) DOS treatment has no influence on MHC class II antigen expression, but induces changes of MHC class I expression. After DOS application in a population of spleen macrophages a subpopulation of cells with reduced MHC class I antigen expression appeared. Down-regulation of these molecules was also observed in immunomorphological studies of kidney graft sections of rats treated with DOS after transplantation; c) after DOS treatment suppressor cells were detected in "suppressor" MLC, 16-33 days after kidney transplantation. Their activity was confirmed 137 days after treatment with DOS, but were inactive in the case of third party cells. These results suggest that DOS action is based on a blockade of antigen presentation by reducing IL-1 production, down-regulation of MHC class I antigen and by inducing suppressor cell population.