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

Radioimmunoassays of human high molecular weight kininogen (HMWK) and low molecular weight kininogen (LMWK) were developed using antibodies directed against the light and the heavy chains of kallikrein-cleaved HMWK. With the anti-light chain antibodies, the radioimmunoassay was specific for HMWK with a detection limit of 0.4 ng. The anti-heavy chain antibodies were used to quantify the concentration of total kininogen antigens. In four different plasmas with a congenital deficiency in HMWK procoagulant activity, there was no detectable antigen in two cases and trace amounts, less than 1 micrograms/ml in the other plasmas (normal concentration: 72 +/- 6 micrograms/ml). In the absence of HMWK, the radioimmunoassay performed with the anti-heavy 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 micrograms/ml, to a normal content. Antigens immunologically indistinguishable from plasma kininogens were detected in lysates of five times washed platelets. HMWK antigen concentration was 3.17 +/- 0.87 micrograms per 10(11) platelets (mean value in 11 donors). LMWK was also present in platelet lysates and the relative concentration versus HMWK was the same as in plasma.