IL-1 acts directly on CD4 T cells to enhance their antigen-driven expansion and differentiation

IL-1 causes a marked increase in the degree of expansion of naive and memory CD4 T cells in response to challenge with their cognate antigen. The response occurs when only specific CD4 T cells can respond to IL-1/β, is not induced by a series of other cytokines and does not depend on IL-6 or CD-28. When WT cells are primed in IL-1R1 ^-/- recipients, IL-1 increases the proportion of cytokine-pro-ducing transgenic CD4 T cells, especially IL-17- and IL-4-producing cells, strikingly increases serum IgE levels and serum lgG1 levels. IL-1β enhances antigen-mediated expansion of in vitro primed Th1, Th2, and Th17 cells transferred to IL-1R1 ^-/- recipients. The IL-1 receptor antagonist diminished responses to antigen plus lipopolysaccharide (LPS) by ≈55%. These results indicate that IL-1β signaling in T cells markedly induces robust and durable primary and secondary CD4 responses.