Interferon-β induces selective enhancement of antigen-specific T cell responses

Interferon-β (IFN-β) inhibits mitogen-induced T cell responses, in part through downregulation of interleukin-12 (IL-12) or upregulation of IL- 10. We have reexamined these findings using ragweed (RW) stimulated or tetanus toxoid (TT)-stimulated human peripheral blood mononuclear cells (PBMC) and nontransformed, antigen-specific, human Th0, Th1, and Th2 clones. IFN-β induced concentration-dependent inhibition of phytohemagglutinin (PHA)-stimulated PBMC proliferation and enhancement of RW-stimulated or TTstimulated PBMC proliferation. Monocyte depletion of PBMC isolates resulted in concentration-dependent inhibition of RW-driven or TT-driven proliferation by IFN-β. This response was unaltered by the addition of either exogenous recombinant human IL-12 (rHuIL-12) or saturating concentrations of anti-IL- 10. Moreover, addition of exogenous rHuIL-10 to nondepleted RW-driven or TT- driven PBMC cultures did not alter the concentration-dependent enhancement of antigen-driven proliferation induced by IFN-β. Th0, Th1, and Th2 clones stimulated in the presence of antigen and autologous, irradiated PBMC displayed concentrationdependent inhibition of proliferation in the presence of IFN-β that was unaltered by the addition of either exogenous rHuIL-12 or a saturating concentration of anti-IL-10. Finally, whereas IFN-β inhibited antigendriven generation of IL-5, IL-12, IL-13, and IFN-γ, IFN-β enhanced generation of both IL-4 and IL-10. Thus, IFN-β induces a selective, IL-10- independent and IL-12-independent upregulation of antigen-specific T cell responses, supporting the role of IFN-β as an immunomodulatory rather than an antiproliferative/immunosuppressive cytokine.