The effect of methylprednisolone prophylaxis on inflammatory monocyte subsets and suppressive regulatory T cells of patients undergoing cardiopulmonary bypass

Cardiopulmonary bypass (CPB) during open-heart surgery triggers an inflammatory response that can cause significant morbidity and mortality. Human monocytes and regulatory T (Treg) cells are phenotypically and functionally heterogeneous and have been shown to play a significant role in the inflammatory dysfunction triggered by CPB. Glucocorticoids (GCs) have been widely administered for decades in patients undergoing CPB to reduce this inflammatory response. However, it has not been clearly established how routine prophylactic administration of glucocorticoids (GCs) affects monocyte and Treg subsets. Thirty-six patient who underwent heart surgery with CPB were randomly assigned to a methylprednisolone group (MG, N = 18; 500 mg in the CPB priming) and a non-methylprednisolone group (NMG, N = 18). The circulating monocyte and Treg subsets were analyzed by flow cytometry. The MG and NMG groups had comparable percentages of monocyte subsets and similar expression levels of HLA-DR, CD86, CD64 and toll-like receptor 4 (TLR4). Remarkably, methylprednisolone increased the percentage of CD4+CD25+ Treg cells among CD4+ T cells in patients undergoing CPB, but did not increase the proportion of suppressive Treg cells, either resting or activated, in these patients undergoing CPB. Our results showed that prophylactic administration of methylprednisolone neither decreased the percentages and counts of inflammatory monocyte subsets nor did it induce the expansion of suppressive Treg cells in patients undergoing CPB. These results clarified the effects of GCs on cell-mediated immune responses and provided additional evidence in practice. Clinicaltrials.gov: NCT01296074. Registered 14 February 2011