Generation of antigen-specific, interleukin-10-producing T-cells using dendritic cell stimulation and steroid hormone conditioning

The mechanisms by which regulatory T-cell populations are generated in vivo are poorly understood. Nonetheless, the possibility of generating T-cells with regulatory capacity ex vivo using pharmacologic agents or modified antigen presenting cells has been raised by a number of recent studies. In this study, the effect of combined glucocorticoid and 1,25 dihydroxyvitamin D₃ (1,25(OH)₂D₃) agonists on dendritic cell (DC)-stimulated, antigen-specific CD4^+ve T-cells was investigated. Following multiple rounds of DC-mediated stimulation in the presence of dexamethasone and an analog of 1,25(OH)₂D₃, the resulting T-cells were characterized by: (a) enhanced IL-10 secretion upon subsequent antigen exposure, (b) attenuated secretion of IL-2 and interferon gamma, (c) lack of induction of Th2 (IL-4-secreting) phenotype, (d) significant antigen-specific suppression of primary T-cell proliferation and (e) retention of the ability to survive and proliferate to antigen in vivo. These IL-10-secreting T-cells were termed 'steroid hormone-conditioned T-cells'. When a co-stimulation-deficient population of DCs was employed for the in vitro, steroid hormone-conditioned stimulations, two additional effects were observed: (a) a further skewing towards antigen-specific IL-10 production and (b) enhanced activation-induced up-regulation of the inhibitory receptor CTLA-4 (CD152). It was concluded that DC-mediated generation of antigen-specific T-cells in vitro can be modulated to promote an IL-10-secreting, regulatory T-cell population using glucocorticoid and 1,25(OH)₂D₃ agonists. This T-cell phenotype can be further enhanced by the use of co-stimulation-deficient DCs.