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