Studies on the Antigenic Determinants of Human Low Molecular Weight Kininogen

The antigenic reactivity of proteins is located in restricted parts of the molecule forming the antigenic determinants that react with the binding sites of the antibody molecule.1 Low molecular weight (LMr) and high molecular weight (HMr) kininogens are immunologically related molecules with common antigenic determinants in the heavy chain of both proteins. 2–4 We have further characterized the nature of these determinants using a kinin-free LMr kininogen isolated from Cohns plasma fraction IV (He antigen). 5,6 shown recently7 the determinant structure of kininogen reside in the polypeptide backbone of the molecule and is not influenced by the partial removal of carbohydrates. This antigen has a heterogeneous light chain which can be isolated after reduction and carboxymethylation. An antiserum produced against the native HC antigen recognizes all native forms of kininogen in human plasma.