Identification of the major chemokines that regulate cell influxes in peritoneal dialysis patients

To investigate which members of the recently discovered family of chemotactic cytokines (chemokines) are important in leukocyte recruitment to a bacterial inflammation site, four different chemokines in the effluent of peritoneal dialysis patients suffering from acute bacterial peritonitis were measured. The presence of two neutrophil-attracting chemokines, interleukin-8 and human melanoma growth-stimulating activity (huGRO alpha), and two monocyte-attracting members of the chemokine superfamily, monocyte chemotactic protein-1 (MCP-1) and regulated on activation normal T cell expressed and secreted (RANTES), was investigated in patient effluents just before, during, and after a peritonitis episode. This was studied in seven peritonitis effluents of five patients by using chemokine-specific enzyme-linked immunosorbent assays. Cell populations in the dialysates were differentiated on cytocentrifuge preparations. The contribution of the detected chemokines to neutrophilic and monocytic cell influxes in the inflamed peritoneal cavity was analyzed by correlating concentrations of chemokines to the relevant cell numbers present in the dialysates of these patients. The detection of the neutrophil-attracting chemokine interleukin-8 during peritonitis was in accordance with other studies. Moreover, a second neutrophil chemoattractant, huGRO alpha, was identified in vivo. Both were elevated during inflammation (P < 0.02) and contributed significantly to the neutrophilic cell influx (P < 0.05). One of the monocyte-attracting chemokines, RANTES, could not be detected in any of the effluents, whereas the other, MCP-1, was significantly elevated during peritonitis (P < 0.02). In contrast to the other chemokines measured, MCP-1 concentration was relatively high in steady-state peritoneal dialysates. An absolute correlation between dialysate MCP-1 concentration and the number of macrophages in these effluents was absent. However, in a 48-well chemotaxis assay, monocyte migration toward peritonitis, as well as steady-state patient dialysates, could be blocked with antibodies to MCP-1. It was concluded, therefore, that MCP-1 is the most important monocyte chemoattractant in peritoneal dialysis steady-state and peritonitis patients; whereas, besides interleukin-8, huGRO alpha was identified as a major neutrophil-attracting chemokine in the peritonitis situation.