Preferential localization and rate of loss of labeled alloantibody from rat tumors and skin transplants carrying the corresponding alloantigen.

125I-Labeled rat histocompatibility antibody was prepared from sera of Buffalo rats immunized with a transplantable fibrosarcoma induced by methylcholanthrene in a Fischer 344 rat. After i.v. injection this antibody was shown to localize with high specificity in transplants of a second Fischer 344 tumor or Fischer 344 skin grafts onto immunosuppressed Buffalo rats. These represent conditions such that only tumor or skin grafts carry the corresponding antigen. In skin transplants localization at 24 hr corresponded to 80% and in tumor to 30% of the injected dose in tissue equal to 1% of the rat weight. However, rapid loss of the 125I label from the target tissues indicated that degradation of antibody fixed to target cells was rapid and that the half-time of the intact antibody was less than 2 days.