Effects of combinatorial in vitro stimulation with glucocorticoids and vitamin D3 on the expression of Foxp3 in CD4+ T cells of healthy individuals

Glucocorticoid (GC) resistance (GR) poses a serious clinical problem affecting a proportion of asthmatic patients. Thus the efforts aimed at exploring therapeutic methods allowing for overcoming GR are still warranted. To date, vitamin D3 was found to exert certain effects indicating that it can potentially supplement the effects of GC therapy in asthmatic patients. Here we wished to investigate whether treatment with GC and/or vitamin D3 can modulate the expression of one of crucial immunomodulatory molecules accounting for suppressive actions of natural regulatory T cells (Treg cells), namely forkhead box P3 (FoxP3). We demonstrated here that 24 h in vitro stimulation with either GC or vit. D3 (alone or in combination) did not significantly affect neither frequencies of CD4+FoxP3+ T cells or the levels of expression of FoxP3 within CD4+ T cells derived from healthy individuals. Therefore we hypothesize that anti-inflammatory actions of both GC and vit. D3 do not seem to be directly related to changes in the expression of FoxP3 in CD4+ T cells.