Description
In addition to helper and regulatory potential, CD4+T cells also acquire cytotoxic activity marked by granzyme B (GzmB) expression and the ability to promote rejection of established tumors. Here we examined the molecular and cellular mechanisms underpinning the differentiation of cytotoxic CD4+T cells following immunotherapy. CD4 transfer into lymphodepleted animals or regulatory T cell (Treg)depletion promoted GzmB expression by tumor-infiltrating CD4+which was prevented by IL-2 neutralization. Transcriptional analysis revealed a polyfunctional helper and cytotoxic phenotype characterized bythe expression of the transcription factors T-bet and Blimp-1. Whilst T-bet ablation restrictedIFN-gproduction, lossof Blimp-1preventedGzmB expressionin response to IL-2, suggesting these are two independent programs required forpolyfunctionality of tumor-reactive CD4+T cells. The data underscores the role of Treg, IL-2 and Blimp-1 controlling the differentiation of cytotoxic T cells and offers a pathway to enhancement of anti-tumor activity through their manipulation.