Antiidiotypic activity in sera from sensitised potential transplant recipients.

Antiidiotypic activity was determined in non-cytotoxic sera from highly sensitised dialysis patients who previously possessed broad-spectrum lymphocytotoxic antibodies. At least four non-cytotoxic sera from six transfused patients were tested in the short antiidiotypic antibody assay against lymphocytes known to be lysed by cytotoxic sera from the same patient. Of 87 sera/cell combinations studied, antiidiotypic activity was detected in 42 (48%). Antiidiotypic activity was present in IgG fractions and F(ab')2 fragments of two active sera. These results indicate that non-cytotoxic sera from patients who were once highly sensitised possess antiidiotypic activity. Fluctuating levels of lymphocytotoxic antibodies frequently encountered in sera from dialysis patients may be explained at least in part by the development of antiidiotypic antibodies.