Radioimmunoassays of human high and low molecular weight kininogens in plasmas and platelets

Abstract

Radioimmunoassays of human high MW kininogen (HMWK) and low MW kininogen (LMWK) were developed using antibodies directed against the L and the H chains of kallikrein cleaved HMWK. With the anti-L chain antibodies, the radioimmunoassay was specific for HMWK with a detection limit of 0.4 ng. The anti-H chain antibodies were used to quantify the concentration of total kininogen antigens. In 4 different plasmas with a congenital deficiency in HMWK procoagulant activity, there was no detectable antigen in 2 cases and trace amounts, less than 1 .mu.g/ml in the other plasmas (normal concentration: 72 .+-. 6 .mu.g/ml). In the absence of HMWK, the radioimmunoassay performed with the anti-H chain antibodies was specific for LMWK. The amount of LMWK was different in each of these patients'' plasmas, ranging from no detectable antigen, i.e., less than 0.15 .mu.g/ml, to a normal content. Antigens immunologically indistinguishable from plasma kininogens were detected in lysates of 5 times washed platelets. HMWK antigen concentration was 3.17 .+-. 0.87 .mu.g/1011 platelets (mean value in 11 donors). LMWK was also present in platelet lysates and the relative concentration vs. HMWK was the same as in plasma.