CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS IMPAIRS T-LYMPHOCYTE SELECTION IN THE PERITONEUM

Peritoneal lymphocytes (PCL) of 45 healthy individuals, four uremic pa tients with end-stage renal disease (ESRD) and 25 long-term continuous ambulatory peritoneal dialysis (CAPD) patients were characterized by how cytometry to investigate whether CAPD alters the phenotype of PCL. B lineage cells constitute a minority of PCL (2.5% of cells). Althoug h the majority of peritoneal T cells expressed alpha beta T cell recep tor (TcR), 7% expressed gamma delta TcR, a proportion which was signif icantly higher than that in peripheral blood (PBMC) (approximately 4%) . The majority of PCL T cells exhibited markers of the thymus-dependen t lineage (CD2, CD3, TcR alpha beta, CD8 alpha beta or CD4) and surfac e antigens associated with memory and activation (CD45RO, CD11a, CD18, CD49d, HLA-DR). An average of 75% of both CD4(+) and CD8(+) PCL T cel ls of healthy subjects and CAPD patients were CDw60(+), thus character izing the T cell subset containing the helper activity for the mitogen -driven B cell differentiation. CD44s was abundantly expressed on PCL T cells. In contrast to PCL T cells of healthy subjects peritoneal T l ymphocytes of CAPD patients exhibited CD44 splice variants containing products of exon-v9 and the proportion of CD44v9(+) cells correlated w ith the frequency of peritonitis episodes the patients had gone throug h. The majority of PCL T cells of both healthy subjects and CAPD patie nts were CD8(+). A large proportion of CD8(+) PCL T cells from healthy subjects expressed the homodimeric CD8 alpha alpha isoform; however, such cells were not found in CAPD patients. In healthy subjects mRNA f or the recombination activating gene 1 (RAG-1) was detectable in a PCL population containing CD7(-)CD34(+) and CD7(+)CD34(+) cells. In contr ast, neither mRNA transcripts of the RAG-1 gene nor CD34(+) cells were detectable in PCL of CAPD patients.