CD46 is a potent co-stimulatory receptor for expansion of human IFN-γ-producing CD8(+) T cells

Similar to CD4(+) T cells, precursor CD8(+) T cells are thought to depend on a co-stimulatory signal through CD28 for proliferation and differentiation into effector cells. CD46 is another co-stimulatory receptor that promotes differentiation of CD4(+) T-helper cells type 1 (Th1 cells) into a regulatory phenotype with a switch from IFN-γ towards IL-10-secretion over time. Whether CD46 exerts a similar function on CD8(+) T cells remains to be fully elucidated. Here, we demonstrate that CD46 co-stimulation induced secretion of IFN-γ as well as expansion of IFN-γ-secreting CD8(+) T cells. In contrast to CD46 co-stimulation of CD4(+) T cells, CD8(+) T cells did not differentiate into a regulatory IL-10-secreting phenotype. This demonstrates that CD46 is a co-stimulatory receptor on CD8(+) T cells, and that it exerts separate functions during CD4(+) and CD8(+) T-cell differentiation.