Effect of interleukin-15 on effector and regulatory function of anti-CD3/anti-CD28-stimulated CD4+ T cells

Autologous transfer of anti-CD3/anti-CD28 ( CD3/CD28)-activated CD4(+) T cells may benefit patients receiving autologous stem cell transplant with severe CD4 lymphopenia. Interleukin ( IL)-15, an IL-2-like cytokine that promotes T cell survival may enhance immune reconstitution in conjunction with adoptive immunotherapy. We investigated the effect of IL-15 on effector and regulatory function of CD3/CD28-activated CD4(+) T cells. IL-15 upregulated CD45RO and CD25 whereas it downregulated CD62L expression of CD3/CD28-stimulated CD4(+) T cells. Both type 1 ( IFN-gamma, tumor necrosis factor ( TNF)-alpha) and type 2 ( IL-5 and IL-10) production by CD3/CD28-activated CD4(+) T cells was further enhanced by IL-15. Co-culture experiments revealed that CD3/CD28-activated CD4(+) T cells downregulated proliferation of autologous peripheral blood lymphocytes ( PBLs) and CD8(+) PBL subsets upon TCR ligation, a contact-dependent effect that was further enhanced by pretreatment with IL-15. Flow cytometric analysis of cell mixture with carboxyfluorescein diacetate succinimidyl ester and Annexin-V-PE staining revealed that CD3/CD28 + IL-15-activated CD4(+) T cells showed increased apoptosis over CD4(+) T cells stimulated with CD3/CD28 alone. Taken together, pretreatment of CD3/CD28-activated CD4(+) T cells with IL-15 may increase regulatory function but may aggravate activation-induced apoptosis of CD3/CD28 CD4(+) T cells.