Accumulating monocytes in the vasculature of rat renal allografts: Phenotype, cytokine, inducible no synthase, and tissue factor mRNA expression

Background. Necrotic patches and hemorrhagic lesions develop in the renal t issue between day 4 and day 5 after transplantation of fully allogeneic DA rat kidneys to LEW recipients. These lesions are at least in part due to de struction and obstruction of blood vessels. Damage of graft endothelial cel ls and blood coagulation are likely to be mediated by intravascular graft l eukocytes. However, this cell population has not been thoroughly characteri zed before. Methods, We perfused untreated control kidneys, renal isografts, and allogr afts on day 4 after transplantation with phosphate-buffered saline/ethylene diaminetetraacetic acid to harvest leukocytes from both the blood stream as well as from the marginal intravascular pool. The mRNA expression of typic al products of activated monocytes was analyzed in reverse-transcriptase po lymerase chain reaction experiments, Graft monocytes were purified and thei r immunophenotype was investigated by flow cytometry, Results, Allograft rejection led to a 10-fold increase in the number of int ravascular graft leukocytes compared to isografts, A mean number of about 1 00x10(6) leukocytes was harvested from a single allogeneic kidney, about 73 % of these cells were monocytes and most of them displayed an activated phe notype, Compared to isografts, intravascular allograft leukocytes displayed an increased expression of tumor necrosis factor-alpha, inducible NO synth ase and tissue factor. Conclusions, Our study shows that large numbers of activated monocytes accu mulate inside allograft vessels. As they express genes the products of whic h might damage the allograft by inducing cell death or thrombosis, me specu late that they directly participate in allograft destruction.