Isolation and characterization of human interleukin-10-secreting T cells from peripheral blood

Recent studies have expanded our understanding of the role of the anti-inflammatory cytokine interleukin (IL)-10, produced by multiple lineages of both human and murine T cells, in regulating the immune response. Here, we demonstrate that the small percentage of circulating CD4⁺ T cells that secrete IL-10 can be isolated from human peripheral blood and, importantly, we have optimized a protocol to expand these cells in both antigen-specific and polyclonal manners. Expanded CD4⁺IL-10⁺ T cells abrogate proliferation and T helper (Th) 1-like cytokine production in an antigen-specific manner, and to a lesser extent exhibit bystander suppressive capacity. CD4⁺IL-10⁺ T cells are suppressive in a cell contact-dependent way, though they do not require secretion of IL-10 for their suppressive role in vitro. CD4⁺IL-10⁺ T cells have an activated phenotype, with high expression of CD25, CD69, and cytotoxic T-lymphocyte antigen-4, and are largely FoxP3 negative. This novel method for the isolation and expansion of suppressive IL-10-secreting T cells has important implications both for further research and clinical therapeutic development.