A method of generating a CD4+FoxP3+ Treg cell, the method includes administering at least one complement antagonist to a naive CD4+ T cell at an amount effective to substantially inhibits C3a receptor (C3aR) and/or C5a receptor (C5aR) signal transduction in the CD4+ T cell, induce TGF-β1 expression of the CD4+ T cell, and induce differentiation of the of the naive CD4+ T cell into a CD4+FoxP3+ Treg cell.