GM AND INV FACTORS IN SUBCLASSES OF HUMAN IGG

Abstract

Human G myeloma (7S γ₂-myeloma) proteins were investigated for relationships between Gm and Inv genetic factors and the different antigenic types of heavy polypeptide chains (γ-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(b²), Gm(f), Gm(b¹), Gm(b³), Gm(b⁴), and Gm(c)], and two Inv factors [Inv(l) and Inv(b)]. Results of the tests were correlated with the four γ-chain subclasses (γ_2a, γ_2b, γ_2c and γ_2d) and the two types of light polypeptide chains, κ-chains (type K or I) and λ-chains (type L or II) found in human IgG molecules. 1. Gm factors were limited to myeloma proteins with heavy polypeptide chains of the γ_2b- and γ_2c-subclasses. No Gm factors were detected on γ_2a- and γ_2d-myeloma proteins or on a "heavy-chain" disease protein of subclass γ_2d. 2. γ_2b-Proteins were positive for at least one Gm factor and were either Gm(a+), Gm(a + x+), or Gm(b²+ f+). 3. γ_2c-Myeloma proteins, and one γ_2c-"heavy-chain" disease protein, were positive for at least one Gm factor and contained various combinations of factors Gm(b¹), (b²), (b⁴), and (c). Myeloma proteins from 3 Negroes were included in this group. 4. Inv factors (l) and (b) were limited to myeloma proteins with κ-light polypeptide chains. These Inv factors were not detected on proteins with λ-light polypeptide chains. 5. Most (70 per cent) of the γ_2b- and γ_2c-proteins with κ-chains were Inv(l+) or Inv(b+). None of the γ_2a- or γ_2d-proteins with κ-chains, however, contained these Inv factors.