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Intensive basic research in immunology has provided us with a detailed understanding of the molecular events and interactions of the immune response that would have seemed incredible only a decade ago. An in-depth knowledge of the factors that initiate and control the immune response is, however, just the first step in learning how to manipulate this complex process for human benefit. One goal that seems quite attainable over the near term is a significant improvement in our ability to alleviate many of the problems resulting from allograft rejection--with newer drugs that not only are more effective, but are also much less hazardous or debilitating to transplant patients. Clearly the goal for the long term is the induction of allograft tolerance, rather than simply the modification of rejection. Genetic techniques will continue to serve as important tools in the research necessary to explore this new territory, and they are even now showing tremendous potential as sources of useful and effective immunotherapies.

In this study donor specific blood transfusion of PVG recipients prevented rejection of DA strain kidneys but, paradoxically, failed to prevent the rapid and progressive accumulation of large numbers of mononuclear cells within enhanced grafts. Morphometric analysis showed that the percentage cellular infiltrate at day 3 was significantly greater in enhanced than in rejecting grafts but a notable feature in the phenotypic analysis of day 5 infiltrates was a markedly reduced number of MRC OX8 positive cells (Tc/s and NK cells) in enhanced grafts. Both rejecting and enhanced allografts showed a marked induction not only of class I but also of class II MHC antigens, and quantitative absorption analysis of donor class I MHC antigens indicated that induction occurred more rapidly in enhanced grafts. Taken together, these findings suggest that blood transfusion sensitizes the recipient, resulting in a more rapid allograft response, but that even in the presence of massive MHC/antigen induction and large numbers of infiltrating cells, immunoregulatory mechanisms are able to suppress the rejection response.