Adaptive plasticity of IL10 + and IL35 + regulatory T cells

Regulatory T cells (T regs) maintain host self-tolerance but are a major barrier to effective cancer immunotherapy. T regs subvert beneficial anti-tumor immunity by modulating inhibitory receptor (IR) expression on tumor infiltrating lymphocytes (TILs); however, the underlying mediators and mechanisms remain elusive. Here we show that interleukin-10 (IL10) and interleukin-35 (IL35; Ebi3/IL12α heterodimer) are divergently expressed by T reg subpopulations in the tumor microenvironment (TME) and cooperatively promote intratumoral T cell exhaustion. T reg -restricted deletion of Il10 and/or Ebi3 resulted in delayed tumor growth, loss of multi-IR expression, and reduced intratumoral CD8 + T cell exhaustion signature. While Il10 or Ebi3 loss was associated with reduced expression of B lymphocyte-induced maturation protein-1 (BLIMP1; Prdm1), IL10 and IL35 differentially impacted effector versus memory T cell fates, respectively, highlighting their differential, partially overlapping but non-redundant regulation of anti-tumor immunity. Our results reveal previously unappreciated cooperative roles for IL10 and IL35, produced by limits effective anti-tumor immunity TIL CD8 cells from Treg specific IL10, IL35 and double knockouts, sorted into populations based on exhaustion markers. TIL Tregs sorted based on IL10 and IL35 expression.