The effects of chronic kidney disease and renal replacement therapy on circulating dendritic cells.

BACKGROUND: The mechanisms underlying the immunodeficiency of chronic kidney disease (CKD) are incompletely understood. Recently, we described decreased numbers of myeloid (m) and plasmacytoid (p) dendritic cells (DCs), considered the most important antigen-presenting cells, in peripheral blood of patients on chronic intermittent haemodialysis (CIHD). In this study, we analysed whether this reduction resulted from CKD or from renal replacement therapy (RRT).
METHODS: Using flowcytometry, we quantified mDCs and pDCs in peripheral blood of patients maintained on CIHD (n = 37), continuous ambulatory peritoneal dialysis (CAPD; n = 29), and patients with CKD not receiving RRT (n = 37). Twenty-nine healthy volunteers served as controls.
RESULTS: Patients with CKD (n = 103) had lower pDC and mDC counts compared with volunteers: 4.2 vs 8.3 and 10.0 vs 13.8 x 10(6) cells/l, respectively (P < or = 0.001). Within the CKD group, pDC counts did not differ between patients on CIHD, CAPD and those not receiving RRT (3.6 vs 5.0 vs 4.9 x 10(6) cells/l, respectively). In the latter group, pDC numbers correlated with the glomerular filtration rate (GFR; Spearman's r = 0.49; P<0.01). In contrast, mDC counts of patients on CIHD were lower compared with patients on CAPD (7.5 vs 10.1 x 10(6) cells/l; P = 0.039) and patients not receiving RRT (13.7 x 10(6) cells/l; P<0.001). Among non-dialyzing patients, no correlation existed between GFR and mDC numbers, which were comparable to those of volunteers, even when only non-dialyzing patients with a GFR below 15 ml/min were analysed.
CONCLUSIONS: Circulating DC counts are decreased in patients with CKD; for pDCs, this reduction is primarily related to the loss of GFR, whereas the dialysis treatment appears to affect mDC numbers.