Inhibition of the mixed leucocyte culture reaction by plasma from renal transplatn recipients.

Plasma samples from 28 renal allograft recipients were studied for the presence of alloantibodies blocking MLC response. MLC blocking antibodies were found in plasma samples obtained from 19 recipients, six with rejected allograft and 13 with long-term surviving transplant. In many instances, these antibodies were found in the absence of detectable lymphocytotoxic antibodies. The MLC blocking activity resides in IgG fractions of plasma samples and was decreased only after absorption with lymphocytes, no effect on blocking was observed by absorption with platelets and fibroblasts.