Masking of Human Transplantation Antigens by Diverse Substances

The reaction of HL-A antibodies with the HL-A determinants on the surface of lymphocytes can be blocked by preincubation of lymphocytes with diverse substances such as normal human serum, autologous plasma, fetal calf serum, newborn serum, heat-inactivated rabbit serum and guinea pig serum, serum albumins from various species, lactalbumin, dextrans, synthetic polyglucose, and polyvinylpyrrolidone. The inhibitors can be washed off readily from lymphocytes. The inhibition procedure described here differs from the conventional inhibition tests in that the inhibitor is added first to the target cells. This “masking inhibition” procedure produces substantially greater inhibition than the standard inhibition methods in which the inhibitor is added first to antiserum before the addition of the target cells. The nonspecific nature of masking inhibition indicates that numerous substances adhere to the lymphocyte surface at HL-A sites or closely adjacent sites.