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Molecular weight of heavy chains of immunoglobulin G typical of cancer is studied immunoglobulin and may be responsible for manifestation of certain anomalous acid and peptide composition of this protein heavy chains as compared with immunoglobulin G in blood serum of healthy people. Immunochemical methods helped detecting an antigenic determinant (or determinants) which is arranged in the heavy chains of the studied immunoglobulin and may be responsible for manifestation of certain anomalous properties of cancer-typical immunoglobulin G molecules. A set of bromo-cyanogenic fragments differing from the spectrum of these fragments in the heavy chains of normal immunoglobulin G is formed following a specific chemical effect of bromo-cyanogen on the heavy chains of immunoglobulin G typical of cancer. Essential differences are found in dancyl-fingerprints of the heavy chains of the compared proteins. Everything mentioned is a result of changes in the primary structure of the heavy chains of immunoglobulin G typical of cancer.

We have analysed reassociated Ig molecules, containing heavy (H) or light (L) chains of Ig-B2 monoclonal antibody with human fibronectin binding activity and L of H chains of normal mouse serum immunoglobulin (Ig-NM). Examination of Ig-B2 idiotype expression in reassociated Ig indicated that 0.4% L-NM and 0.8% H-NM were able to restore Ig-B2 idiotype. The analysis of antigen binding capacity of reassociated Ig demonstrated, that only 4% H-NM created antigen binding site in complex with L-B2. We have determined the leading role of L-chain in creation of idiotype and binding site of Ig-B2. Selectivity of interaction between H and L chains is discussed. The results indicate, that not more than 4-6% of random H--L combinations produce functional Ig.