Dendritic cell subset ratio in tolerant, weaning and non-tolerant liver recipients is not affected by extent of immunosuppression

Dendritic cell (DC) subsets regulate alloimmune responses and may play a role in transplant tolerance. We extend an analysis of circulating precursors (p) of CD11c(+) CD123(-/lo) (IL-3Ralpha(-/lo)) (pDC1) and CD11c(-) CD123(hi) (pDC2) DC subsets in primary cadaveric liver allograft recipients. Additionally, we examine DC subset levels in relation to the nature and extent of immunosuppressive therapy. The data consolidate the finding that the pDC2/pDC1 subset ratio is significantly higher in patients on minimal calcineurin inhibitor monotherapy undergoing successful weaning (n = 36) and in those off all anti-rejection therapy (n = 18) compared with patients on maintenance immunosuppression (n = 21). No relationship was found between the incidence of either pDC subset or the pDC subset ratio and time post-transplant or time off immunosuppression in any group. There was also no correlation between the pDC subset ratio and either prednisone or tacrolimus dose or tacrolimus trough blood level. No evidence was found that combination of these drugs influenced the incidence of pDC2 relative to pDC1. Thus, a greater prevalence of pDC2 in stable liver recipients on low dose anti-rejection therapy or in those off immunosuppression, compared with that in patients on maintenance immunosuppression, does not reflect a differential effect of anti-rejection drugs on pDC subsets.