A Human Antibody to Gm (26): An Antigen Usually Present on the γ‐3 Chain of IgG When Gm (15) is Absent1

Abstract

An antibody to an antigen on IgG was found in the serum of a healthy American Negro, whose phenotype is Gm (1, 13, 15, 17). (When tested for Gm [1, 2, 3, 5, 6, 13, 15, 16, 17, 21].) Subsequent tests of serum samples from US blacks and whites, from Japanese, Ainu, San (Bushmen), Negros, Asiatic Indians and Jews from Cochin India demonstrated that the antibody detects an antigen that is usually present in a haplotype when Gm (15) is absent from it. This antigen had been identified using an antibody produced in a baboon. Tests of isolated myeloma proteins and of Fc and Fab fragments of IgG confirmed that the antigen [Gm (26) or Gm (u) - originally Gm (Pa)] is carried by the Fc portion of the gamma3-chain.