PHENOTYPE OF RAT MONOCYTES DURING ACUTE KIDNEY ALLOGRAFT-REJECTION - INCREASED EXPRESSION OF NKR-P1 AND REDUCTION OF CD43

Monocytes and macrophages mediate cytotoxicity after appropriate activ ation and thus represent effecters secondary to T lymphocytes and natu ral killer (NK) cells. However, very little is known about the role of activated monocytes in organ allograft rejection. Tn this study, isog eneic (LEW to LEW) and fully allogeneic (DA to LEW) rat kidneys were g rafted to bilaterally nephrectomized recipients. Four days after trans plantation a comprehensive sample of leucocytes was recovered by perfu sion of the recipients' vasculature with phosphate-buffered saline con taining EDTA (PBS/EDTA). Monocytes were enriched by density gradient c entrifugation and their physical parameters and immunophenotype were i nvestigated by flow cytometry in comparison with untreated, specified pathogen-free (SPF) LEW rats. Isotransplantation and allotransplantati on of kidneys dramatically increased the absolute number of intravascu lar monocytes in the recipient. Analysis of NKR-P1 (CD161), CD4, CD62L , CD43, CD11a, CD18 and MHC class II expression identified at least tw o monocyte populations in all experimental groups. In graft recipients it was evident that activated monocytes were able to express and upre gulate NKR-P1 and CD8, which have not been detected in these cells to date. If activated monocytes utilize NKR-P1 and CD8, by analogy to NK cells and lymphocytes these cells may be endowed with additional pathw ays to upregulate cytolytic functions and effect allograft damage.