a-f. Representative flow cytometric plots show gating strategies for naïve T cell sorting (a), Th9 sorting for transfer experiments (b), for in vitro differentiated Th9, Th1, and Th2 cells shown in Figures 1-3 and S1-S3 (c), for in vivo memory T helper subsets in Figures 5-6 and S5-S6 (d-e), and for adoptively transferred CD45.1+ Th9 cells analyzed in murine lung two days after transfer (f). g. Timeline shows protocol for validation of MHC2 blocking antibody in vivo. Mice were sensitized to ovalbumin (OVA) intraperitoneally on d0 and d7, then challenged on d13 and d14. MHC blocking antibody was administered with each dose of OVA. Bar graphs show results of MHC2 validation experiment. Blockade of MHC2 reduced histology scores, BAL Eosinophil counts, and lung-infiltrating IL-4+ and IL-13+ (Th2) cell counts. Mean ± SEM, 2-sided Mann Whitney, all data points represent biological replicates.