IgM xenoantibody response in C57BL/6 nude, BALB/c nude, and CB17SCID mice given BALB/c nude splenocytes. (A) Naive nude animals were either immunized with hamster RBCs (C57BL/6, n = 7; BALB/c, n = 3) or given a hamster xenoheart (C57BL/6, n = 7; BALB/c, n = 6). Serum hamster-specific IgM xenoantibodies were assayed either on day 7 (hamster RBC), or between days 2 and 6 (C57BL/6, at the time of xenograft rejection), or between days 3 and 12 (BALB/c, no rejection of xenografts). One C57BL/6 nude group was given 2 Gy TBI 1 week before hamster RBC immunization (n = 6). Naive BALB/c nude (n = 12) and C57BL/6 nude (n = 9) animals were used as controls. Bars represent the mean (± SE) MFI values. *P < .05; NS indicates not significant for comparison between groups. (B) Histograms illustrating IgM xenoantibody serum levels of naive (top panels) or hamster RBC–immunized (bottom panels) nude C57BL/6, nude BALB/c, or CB17 SCID mice (MFI is indicated in the top right corner). (C) Histogram illustrating IgM xenoantibody serum levels of CB17 SCID mice after transfer of 120 × 106 BALB/c nude splenocytes on day −14. Serum IgM xenoantibodies were determined on day 7 relative to hamster RBC immunization (1 of 2 identical experiments is shown).
