Antimurine immunoglobulin antibody responses after the administration of murine monoclonal antibodies to rats are altered by small bowel allograft rejection

Background. This study monitored the induction of antimurine immunoglobulin antibody responses after the administration of anti-CD4 (OX38) and anti-LF A-1 (WT.1) monoclonal antibodies to DA rats. Methods. Monoclonal antibody was administered i.v. on 3 consecutive days to untransplanted DA rats, and DA recipients of PVG small bowel allografts. C ontrol animals received no monoclonal antibody. Antimurine immunoglobulin a ntibody levels in serum samples were determined by enzyme immunoassay. Results. No antimurine immunoglobulin antibody was detected in untransplant ed animals receiving OX38 alone. Reactivity was apparent in WT.1-treated an imals, but this response was totally abrogated by the co-administration of OX38. A combination of OX38 and WT.1 had no effect on allograft recipient s urvival and antimurine immunoglobulin antibody responses were detected in a ll allograft recipients, irrespective of the treatment regimen. Conclusions. Although OX38 inhibited the antibody response both to itself a nd to WT.1 in untransplanted animals, the immune reaction induced by small bowel allograft rejection overcame this inhibitory capacity.