A study of innate immunity in patients with end-stage renal disease: special reference to toll-like receptor-2 and -4 expression in peripheral blood monocytes of hemodialysis patients.

It was recently shown that toll-like receptors (TLR) play a critical role in innate immunity. However, no study has been conducted on TLR expression in hemodialysis (HD) patients. The present study was undertaken to examine innate immunity and the roles played by endotoxins (ET) contained in dialysate in HD patients, by analysis of TLR expression and reactivity. TLR-2 and TLR-4 expression on monocytes was investigated by flow cytometry in the following groups of subjects: healthy controls, patients on HD, patients with end-stage renal disease (ESRD) and patients on peritoneal dialysis (PD). The expression of TLRs on monocytes under stimulation with lipopolysaccharide was also investigated. Expression of TLR-4 was lower in the HD group than in the healthy controls (p<0.05), while expression of TLR-2 was lower in the PD group than in the healthy controls (p<0.05). As the duration of dialysis became longer, TLR-4 expression decreased (p<0.01). TLR-2 was not correlated with duration of dialysis, and the magnitude of decrease in TLR-4 expression following stimulation with ET became smaller (p=0.0006). Suppression of expression of TLR-4 was noted in HD patients, and TLR-4 expression was reduced as the duration of dialysis became longer. Reduced TLR-4 expression may be associated with the compromised immune function in HD patients. It seems possible that chronic stimulation with ET suppresses the expression of TLR-4.