Identification of ICAM-1-positive cells in the nongrafted and transplanted rat kidney--an immunohistochemical and ultrastructural study.

Cellular localization of intercellular adhesion molecule-1 (ICAM-1) in rat nongrafted intact kidneys and in transplanted kidneys was investigated using monoclonal anti-rat ICAM-1, 1A29. The major ICAM-1-positive cells in the nongrafted and isografted kidneys were endothelial cells in the large vessels and intertubular capillaries, as observed using light microscopy. A weak, but specific expression of ICAM-1 antigen was noted in the glomeruli, but the exact localization and cell type were not clearly discernible. In the allograft, the ICAM-1-positive cells found in the nongrafted and isografted kidneys also expressed ICAM-1 antigen. In addition, tubular epithelial cells at the luminal border and some infiltrating cells in the allograft expressed ICAM-1. In the allograft, some graft-infiltrating cells were shown to be lymphocyte function-associated antigen-1(LFA-1)-positive. As the nature of ICAM-1-positive cells in the infiltrates was unclear, we examined ICAM-1-positive cells using immunoelectron microscopy and the direct immunoperoxidase method. Glomerular endothelial cells, podocytes, and Bowman's capsular epithelial cells expressed ICAM-1 antigen in the nongrafted and transplanted kidneys. Among the infiltrating cells in the allograft, the major ICAM-1 positive cells were macrophagelike tissues, and some blastic lymphocytes also expressed ICAM-1. Only rarely did the proximal tubular cells express ICAM-1 antigen at the luminal surfaces in the intact kidney. In the allograft, the proximal, distal, and collecting ductular epithelial cells expressed ICAM-1 at the luminal surface, and in addition, the ICAM-1 antigen was also localized at the basal surfaces of some of the renal proximal tubular epithelial cells. The upregulated ICAM-1 expression in the allograft may accelerate graft rejection by augmenting adhesiveness of LFA-1-positive graft-infiltrating cells.