Fig. 1

Under conditions of competition, GITR is intrinsically required for the accumulation of effector CD4 and CD8 T cells during influenza infection. a Schematic indicating that lethally irradiated Thy1.1 CD45.2 hosts were reconstituted with a 1:1 mixture of GITR^−/− Thy1.2 CD45.2: GITR^+/+ Thy1.2 CD45.1 bone marrow cells. Chimeric mice were rested for 90 days and chimerism checked in the blood of each mouse, before intranasal (i.n.) infection with influenza A/HK-X31 followed by analysis at day 7 or day 10 post infection (p.i.). b Representative gating strategy for donor CD44^hi T-bet⁺ Th1, CD25^hi FoxP3⁺ Treg, and tetramer⁺ CD8 T cells. c Representative flow cytometry plots showing proportions of GITR^+/+: GITR^−/− of blood CD4 T cells before infection and of lung Th1 day 10 p.i. The normalized GITR^+/+: GITR^−/− ratio in Th1 d and Treg e compartments was evaluated in the lung, mediastinal lymph node (mLN), and spleen day 7 or day 10 p.i. Normalization was done by dividing the post-infection ratio in each mouse in each tissue by the pre-infection ratio of CD4 T cells in blood from the same mouse. f The normalized GITR^+/+: GITR^−/− ratio in CXCR5⁺ PD-1⁺ FoxP3⁻Tfh compartment was evaluated in the mLN and spleen day 7 p.i. and normalization was done as described above. Representative gating for donor Tfh is shown on the left. g Representative flow cytometry plots showing proportions of GITR^+/+:GITR^−/− of blood CD8 T cells before infection and of lung D^b/PA_224–233-specific CD8 T cells day 10 p.i. The normalized GITR^+/+:GITR^−/− ratio in D^b/NP_366–374-specific CD8 T cell h and D^b/PA_224–233-specific CD8 T cell i compartments was evaluated in the lung, mLN, and spleen day 7 or day 10 p.i. Normalization was done using pre-infection ratio of blood CD8 T cells as described for CD4 T cells above. Each symbol represents an individual mouse, with bars indicating median with interquartile range (IQR). Statistical analyses performed using Wilcoxon test comparing pre- and post-infection ratios. Data are pooled from 11 to 16 individual chimeric mice from at least two independent experiments