Immunomodulating properties of the uremic pentapeptide H-Asp-Leu-Trp-Glu-Lys-OH in vitro.

A pentapeptide originally isolated by Abiko and coworkers from the ultrafiltrate of a uremic patient was synthesized and studied for its in vitro effects on normal human peripheral blood mononuclear cells. The SRBC-rosette forming capacity of T cells was significantly reduced after preincubation of the cells with the peptide, whereas the viability and the percentage of SRBC-receptor positive cells as determined with a monoclonal antibody remained unchanged. The PHA and ConA induced proliferation of T cells as well as the induction of suppressor cells by ConA were decreased, while the proliferative responses to PWM and specific antigens were enhanced. MLC experiments with separated and reconstituted lymphocyte populations pointed to the T cell as the main target. The data presented demonstrate that at least some of the effects described for so-called middle molecules are reproducible with this peptide at concentrations eventually occurring in patients with chronic renal failure.