Segregated Regulatory CD39+CD4+ T Cell Function: TGF-β–Producing Foxp3− and IL-10–Producing Foxp3+ Cells Are Interdependent for Protection against Collagen-Induced Arthritis

Abstract

Oral immunization with a Salmonella vaccine vector expressing enterotoxigenic Escherichia coli colonization factor Ag I (CFA/I) can protect against collagen-induced arthritis (CIA) by dampening IL-17 and IFN-γ via enhanced IL-4, IL-10, and TGF-β. To identify the responsible regulatory CD4+ T cells making the host refractory to CIA, Salmonella-CFA/I induced CD39+CD4+ T cells with enhanced apyrase activity relative to Salmonella vector-immunized mice. Adoptive transfer of vaccine-induced CD39+CD4+ T cells into CIA mice conferred complete protection, whereas CD39−CD4+ T cells did not. Subsequent analysis of vaccinated Foxp3-GFP mice revealed the CD39+ T cells were composed of Foxp3-GFP− and Foxp3-GFP+ subpopulations. Although each adoptively transferred Salmonella-CFA/I–induced Foxp3− and Foxp3+CD39+CD4+ T cells could protect against CIA, each subset was not as efficacious as total CD39+CD4+ T cells, suggesting their interdependence for optimal protection. Cytokine analysis revealed Foxp3− CD39+CD4+ T cells produced TGF-β, and Foxp3+CD39+CD4+ T cells produced IL-10, showing a segregation of function. Moreover, donor Foxp3-GFP− CD4+ T cells converted to Foxp3-GFP+ CD39+CD4+ T cells in the recipients, showing plasticity of these regulatory T cells. TGF-β was found to be essential for protection because in vivo TGF-β neutralization reversed activation of CREB and reduced the development of CD39+CD4+ T cells. Thus, CD39 apyrase-expressing CD4+ T cells stimulated by Salmonella-CFA/I are composed of TGF-β–producing Foxp3− CD39+CD4+ T cells and support the stimulation of IL-10–producing Foxp3+ CD39+CD4+ T cells.