Figure 6. Type I IFNs Act on DCs to Suppress Development of Antigen-Specific CD4⁺ T Cells.

(A) A 90:10 mix of B6.CD45.1/CD45.2 and Ifnar1^−/− (CD45.2) BM cells was engrafted into lethally irradiated CD45.1 recipients.

(B) Following 10–12 weeks of engraftment, chimeric mice were infected with L. donovani, and 14 days later, spleen and liver mononuclear cells were isolated to assess the activation status of control B6 (CD45.1/CD45.2) and Ifnar1^−/− (CD45.2) CD4⁺ T cells from the same mouse using the gating strategy shown.

(C) The frequency of splenic and hepatic CD4⁺ T cells recently activated by parasite antigen (CD11a^hi/CD49d^hi), Th1 cells, and Tr1 cells (gated as shown in Figure S2) was measured by flow cytometry, as indicated.

(D) Ifnar1^ΔDC mice generated by crossing Cd11c-Cre mice with Ifnar1-floxed animals were infected with L. donovani, and 14 days later, Th1 cell number and frequency as well as parasite burden in the spleen and liver were measured, as indicated.

n = 4–10 mice per group. Experiments were conducted 3 times. Mean ± SEM (C and D), *p < 0.05; significance assessed by Mann-Whitney test.