Indirect antigen presentation leads to in utero and neonatal demise after IUHCTx. (A) B6 mothers were bred to either 4C males (B6 mice with CD4 T cells recognizing I-Ad presented on BALB/c MHC class II, direct pathway) or (B) TCR75 males (B6 mice with CD4 T cells recognizing H-2Kd presented on B6 MHC class II, indirect pathway) and transplanted with BALB/c fetal liver hematopoietic cells. Flow cytometric analysis was used to genotype (A) 4C (CD4+Vβ13+) and (B) TCR75 (loss of bimodal distribution of Vβ8) transgenic animals. (C) The overall litter survival rate, including both wt and TCR-Tg pups. 4C, n = 37; TCR75, n = 83 injected. (D) Relative proportion of wt pups (plain bars) and TCR-Tg pups (diagonal bars) within each litter. 4C, n = 29; TCR75 with IUHCTx, n = 28; TCR75 without IUHCTx, n = 38. (E) The rate of chimerism of wt and TCR-Tg animals at 2 to 3 weeks after IUHCTx. TCR75, n = 8; 4C, n = 8; wt littermates, n = 26. P values: *<.05; **<.01 by χ2 test. wt, wild type.