A PEPTIDE ISOLATED FROM A PATIENT ON CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS HAS HOMOLOGY TO UBIQUITIN AND INHIBITS THE CHEMOTACTIC RESPONSE OF POLYMORPHONUCLEAR LEUKOCYTES

Susceptibility to bacterial infections in the peritoneal cavity is a s erious problem for peritoneal dialysis patients. Uremic toxins are amo ng the causes of the diminished function of polymorphonuclear leuckocy tes (PMNLs), cells of the local immune defense. We isolated from the p eritoneal dialysis effluent of a uremic patient, a peptide that inhibi ts PMNL chemotaxis in a concentration-dependent manner. The amino term inus of this factor is identical to that of ubiquitin. The peptide sho ws the same size as ubiquitin on SDS-polyacrylamide gels, but has a mo re acidic isoelectric point than intact ubiquitin, which has no effect on PMNL chemotaxis. We conclude that we have isolated a modified form of ubiquitin and that this modification is responsible for its inhibi ting effect on PMNL chemotaxis.