EFFECT OF SKIN ALLOGRAFTS ON RETICULOENDOTHELIAL SYSTEM

Further evidence has been provided that skin allografts stimulate the reticuloendothelial system (RES) as indicated by an increased rate of clearance of 32P-labelled Salmonella typhimurium (C5) from the circulation, and it has been shown that the magnitude of this increase is directly related to the size of the graft employed. Splenomegaly was observed in allografted mice and this, as with the increased rate of clearance of labelled bacterial particles, occurred just prior to macroscopic rejection of the graft. Splenectomy did not, however, alter the subsequent survival of the graft or the changes in the RES activity. The distribution of the radioactive label indicated that the phagocytic cells of the liver were primarily responsible for the increased rate of clearance observed. This increased rate, of clearance, which reflected one aspect of RES activity, was not paralleled by an increased ability of such an animal to produce antibodies when challenged with another antigen. The demonstration of changes in phagocytic activity following removal of the graft at varying intervals and the relationship of this response to macroscopic and histological graft rejection indicate that the release of antigens from the graft stimulates the RES rather than the graft rejection per se. This is not a direct effect of the antigens on the cells of the RES but is caused by a factor released by the lymphoid cells after their interaction with the antigen. These studies have also shown that the measurement of phagocytic activity may be utilized to indicate the presence of a host-versus-graft reaction. © 1969 by The Williams and Wilkins Co.