Increasing recipient TCR clonotypic variety reduces penetrance and severity of cGVHD. Combined data from 2 experiments. On day 0, recipient mice were lethally irradiated and reconstituted with 8 × 10⁶ BM cells alone (n = 29, all recipient types) or BM plus 10⁷ spleen cells: WT (n = 29), DO11.10 (RAG2^+/+) (n = 12), DO11.10 (RAG2^-/-) (n = 18), RAG2^-/- (n = 16). (A) Incidence of cGVHD. ^*P < .05 for DO11.10 (RAG2^+/+) versus WT and versus RAG2^-/-; P = .094 for DO11.10 (RAG2^+/+) versus DO11.10 (RAG2^-/-). (B) Pathology score for representative mice. Mean score is indicated by a horizontal bar. ^*P < .05 for DO11.10 (RAG2^+/+) versus DO11.10 (RAG2^-/-) and versus RAG2^-/-. Pathology samples were taken on day 24, 28, or 50.