mRNA expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in acute renal allograft rejection

Background. The intercellular adhesion Molecule-1 (ICAM-1) and the vascular cell adhesion molecule-1 (VCAM-1) show a form of complementary distributio n in normal and grafted kidneys. The molecular mechanism by which ICAM-1 an d VCAM-1 are increased or induced on vascular cells during acute renal allo graft rejection has not been clearly defined. Methods. We examined ICAM-1 and VCAM-1 mRNA expression in 17 renal allograf t biopsies with (n=12) and without (n=5) features of acute rejection, and f our control renal biopsies with no detectable abnormalities by RNA in situ hybridization. The expression of ICAM-1 and VCAM-1 protein was also assesse d by immunohistochemical staining of frozen sections. Results. In controls and nonrejecting graft biopsies, the signals of the IC AM-1 and VCAM-1 transcripts in vascular cells were almost negligible. Speci fic signals of ICAM-1 and VCAM-1 mRNAs were detected on the endothelial cel ls of small muscular arteries in most cases with acute renal allograft reje ction. The messages for ICAM-1 and VCAM-1 were also detected on arterial sm ooth muscle cells in all the five cases with severe type III rejection. Conclusions. These results suggest that the induced appearance of ICAM-1 an d VCAM-1 on the vascular cells of acutely rejecting renal transplants was r elated to actual cellular synthesis and that both adhesion molecules could act together in the rejection process. They also suggest that the expressio n of ICAM-1 and VCAM-1 genes by arterial smooth muscle cells may be an impo rtant cause of transmural arteritis in severe acute renal allograft rejecti on.