GM and INV factors in subclasses of human IgG.

Human G myeloma (7S gamma(2)-myeloma) proteins were investigated for relationships between Gm and Inv genetic factors and the different antigenic types of heavy polypeptide chains (gamma-chains) and light polypeptide chains. Myeloma proteins were isolated from the sera of 1 Chinese, 60 white and 28 Negro individuals. These 89 proteins were tested for eight Gm factors [Gm(a), Gm(x), Gm(b(2)), Gm(f), Gm(b(1)), Gm(b(3)), Gm(b(4)), and Gm(c)], and two Inv factors [Inv(l) and Inv(b)]. Results of the tests were correlated with the four gamma-chain subclasses (gamma(2a), gamma(2b), gamma(2c) and gamma(2d)) and the two types of light polypeptide chains, kappa-chains (type K or I) and lambda-chains (type L or II) found in human IgG molecules. 1. Gm factors were limited to myeloma proteins with heavy polypeptide chains of the gamma(2b)- and gamma(2c)-subclasses. No Gm factors were detected on gamma(2a)- and gamma(2d)-myeloma proteins or on a "heavy-chain" disease protein of subclass gamma(2d). 2. gamma(2b)-Proteins were positive for at least one Gm factor and were either Gm(a+), Gm(a + x+), or Gm(b(2)+ f+). 3. gamma(2c)-Myeloma proteins, and one gamma(2c)-"heavy-chain" disease protein, were positive for at least one Gm factor and contained various combinations of factors Gm(b(1)), (b(2)), (b(4)), and (c). Myeloma proteins from 3 Negroes were included in this group. 4. Inv factors (l) and (b) were limited to myeloma proteins with kappa-light polypeptide chains. These Inv factors were not detected on proteins with lambda-light polypeptide chains. 5. Most (70 per cent) of the gamma(2b)- and gamma(2c)-proteins with kappa-chains were Inv(l+) or Inv(b+). None of the gamma(2a)- or gamma(2d)-proteins with kappa-chains, however, contained these Inv factors.