Figure 5. T_FR regulate the size of the T_FH population.

Flow cytometric contour plots and graphs of T_FH cells (a) and germinal center B cells (b) from the spleens of Foxp3^DTR mice immunized eight days previously (d0) with SRBC. Five days after immunization the mice were treated with either DT or saline. (c-f) Analysis of mixed bone marrow chimeras generated by sub-lethally irradiating Rag2^−/− mice and reconstituting their immune system with either a 1:1 ratio of Sh2d1a^−/− CD45.2 : Foxp3^DTR CD45.1 bone marrow or control Sh2d1a^+/+ CD45.2 : Foxp3^DTR CD45.1 bone marrow. Eight weeks after reconstitution chimeric mice were immunized with SRBC and treated with 50μg/Kg of DT on one day prior to immunization and d2 and d5 thereafter. Splenocytes were analyzed on d8 for the proportion and total number of CD4⁺CXCR5^highPD-1^highFoxp3⁺ T_FR cells (c), CD4⁺Foxp3⁺ T_reg (d), CD4⁺CXCR5^highPD-1^high T_FH cells (e) and B220⁺ GL-7^highCD95^high germinal center B cells (f). Each symbol represents one mouse and horizontal bars represent median values. Statistical significance was determined using a Mann-Whitney Test: *P<0.05, **P<0.01.