Normal IEL precursor development and intestinal homing in the absence of GPR18. (A) Mixed BM chimeras of the type in Fig. 2 were analyzed for Vγ7⁺ γδT cells in thymus and mLN. Thymic cells were gated as CD8⁻CD4⁻TCRβ⁻ γδTCR⁺Vγ7⁺ and mLN cells as TCRβ⁻ γδTCR⁺Vγ7⁺, and the data are plotted as the ratio of gated cells that were CD45.2⁺ (Gpr18^+/− or Gpr18^−/−) versus CD45.1/2⁺ (WT). (B) IELs from Gpr18^+/− (CD45.1⁺) and Gpr18^−/− (CD45.1/2⁺) mice were co-transferred into Ccr9^−/− recipients. 20 h later, the distribution of transferred CD8αα γδT IELs in blood (Bd) and intestine IELs was analyzed by flow cytometry. The plot on the right shows the ratio of Gpr18^−/− versus Gpr18^+/− donor cell frequencies in blood and IELs, summarized from three experiments. (C) LN T cells from WT (CD45.1/2⁺) and Ccr9^−/− (CD45.2⁺) mice were stimulated with CD3/CD28 plus retinoic acid and co-transferred into CD45.1⁺ WT hosts. 20 h later, the distribution of transferred CD8 T cells in blood and IELs was analyzed by flow cytometry. Data are representative of three or more experiments in A and B and of two mice in C. In A and B each symbol represents an individual mouse, and the horizontal lines indicate the mean.