Antigen level, OX40 (CD134) and 4-1BB (CD137) costimulation, and IL-33 support CD4 T cell differentiation and functionality (IRC8P.448)

Abstract We set out to determine how costimulation induces cytotoxic CD4 T cells. In our in vivo model, CD11c+ cells express varying levels of Eα antigen linked to MHC II. To study CD4 T cell differentiation we transferred in Eα-specific T cells and monitored functionality. Mice were treated with OX40 and 4-1BB agonists, and cytotoxic CD4 T cells were assessed. In high antigen presenters (Eαhi) the T cells became primarily T-bet+ GzmB+ IL-33R++ and clonally expanded, while low antigen presenters (Eαlo) induced T cells that were mostly Gata3+ or Eomes+ KLRG1+ IL-33R+ with reduced expansion levels. Upon ex vivo stimulation with Eα, T cells from Eαhi mice produced higher IFNɣ levels than T cells from Eαlo mice, whereas IL-4 levels were low in both. Since IL-33R was expressed, we showed that higher IL-33R on specific T cells from Eαhi mice conferred greater production of IFNɣ by demonstrating that IL-33 synergized with IL-2, IL-12 and IL-36β independent of TCR signals. The decreased functionality of T cells from Eαlo mice may be due to more Tregs since exhaustion markers were unexpectedly higher on T cells from Eαhi mice. These novel findings demonstrate that 1) cytotoxic CD4 T cells can be induced by costimulation therapy but may be a heterogeneous population, 2) antigen presentation levels have a substantial effect on T cell differentiation programming and 3) IL-33 can act as a Th1 activating cytokine. Thus, this data will greatly impact CD4 T cell immunotherapeutic approaches.