The in vitro synthesis of subclasses of human gamma-G as demonstrated by a study of allotypes. The genes of the Gm system are they structural genes?

Production of γG-immunoglobulins by lymphocytes cultured in the presence of phytohaemagglutinin has been demonstrated by a study of some allotypes of the Gm system. For certain donors, the phenotype of the supernatant after culture (72 or 96 hours) corresponded to the serum phenotype. For one subject, only the Gm(4) factor was demonstrated, while the Gm(5) factor was nevertheless present in the serum. In other cultures, it was possible to show only the presence of the Gm (4 and 5) and Gm (1 and 4) factors, though the individuals possess the Gm (1, 4, 5 and 17) serum phenotypes. These results indicate that the synthesis of the γG1 Gm(1, 17), γG1 Gm(4), or γG3 molecules may not be simultaneous. However, they may also reflect synthesis by the only clones that survived. In six of the individuals with the Gm (–1, –2, 4, 5, –17) phenotype, a study on supernatants after culture revealed the presence of factors which do not exist in the serum: the Gm (1 and 17). This result confirms what Lobb, Curtain and Kidson (1967) and Lobb (1968) have demonstrated by immunofluorescence, and raises a problem as to the existence of regulatory genes.