sigmodontis infection. As SAHA HDAC a first approach to dissect the role of the different IL-10-producing cell types in suppressing L. sigmodontis-specific Th1 and Th2 immune responses, we used mice with targeted B-cell-specific (IL-10FL/FL CD19-Cre) and CD4+ T-cell-specific (IL-10FL/FL CD4-Cre) deletion of the IL-10 gene [23, 24]. The immune response provoked by natural L. sigmodontis infection in mice lacking either T-cell-derived or B-cell-derived IL-10 was analyzed at days 17, 30, or 60 p.i. Recording L. sigmodontis

Ag-specific Th1 and Th2 responses, we observed that IL-10 deficiency in CD4+ T cells resulted in increased production of both, Th1-associated IFN-γ and Th2-associated IL-5 plus IL-13 responses to L. sigmodontis Ag at day 17 as an early time point of infection and at day 60 p.i. as a late time point of infection (Fig. 2A). Increased cytokine production was also observed upon polyclonal T-cell stimulation by anti-CD3 in CD4+ T-cell-specific IL-10−/− mice. CD19+ B cells represented a major source of L. sigmodontis-specific IL-10 during infection (Fig. 2, days 17 and 60). Interestingly, this B-cell-derived IL-10 was not mediating suppressive BTK inhibitors library effects, since B-cell-specific IL-10 deficiency did not induce statistically significant changes in L. sigmodontis Ag-specific

cytokine responses throughout infection (Fig. 2A). Polyclonal T-cell stimulation resulted in comparable, but low proliferation in splenocytes derived from all groups at day 60 p.i. L. sigmodontis Ag-specific proliferation was detectable Branched chain aminotransferase in WT mice, while increased by trend in mice lacking IL-10 in T cells and decreased by trend in mice lacking IL-10 in B cells. However, these changes were not statistically significant (Fig. 2B). To rule out that the increased cytokine production observed in T-cell-specific IL-10−/− mice was due to changes in the cellular composition, we analyzed spleens at day 60 p.i. We did not record

significant changes in number and frequency of CD19+ B cells (Supporting Information Fig. 1A). We observed a decreased number and frequency of all T cells including CD4+Foxp3+ regulatory T cells, CD4+ T cells, and CD8+ T cells in spleens derived from T-cell-specific IL-10−/− mice (Supporting Information Fig. 1B). Therefore, increased Ag-specific proliferation and cytokine production in these mice was initiated by an even lower number of CD4+ T cells. The number and frequency of DX5+CD3− NK cells or DX5+CD3+ NKT cells were unchanged in all strains (Supporting Information Fig. 1C). Neither B-cell- nor T-cell-specific IL-10 deficiency induced statistically significant changes in the humoral response (Supporting Information Fig. 2). Taken together, our results indicate that specifically T-cell-derived IL-10 interfered with L. sigmodontis-specific Th1 and Th2 responses. B-cell-derived IL-10 was not central for initiating L.