Significant reduction of in vivo donor antihost cytotoxic response after HVEM/BTLA blockade. Recipient F1 mice were adoptively transferred with 70 × 106 of B6 splenocytes and treated with either isotype control (rat IgG2a, 1 mg), anti-HVEM (nonblocking, clone 1H7, 1 mg), or anti-HVEM (blocking, clone 6C9, 1 mg) mAbs. Sixteen days later, recipient mice received 30 × 106 splenocytes of each CFSE-labeled target cell, as follows: B6 (0.4 μM), BALB/c (2 μM), and F1 (10 μM). The percentage of specific lysis in spleen (A) and peripheral lymph node (inguinals plus axilars) (B) was calculated at 72 h, according to the equation described in Materials and Methods. Data are representative of two independent experiments with three mice per group. Bars indicate mean ± SEM, and t test was used to compare differences between groups. Statistical significance was indicated, as follows: ***p < 0.0005.