Serological Properties of gammaG and gammaM Antibodies to the Somatic Antigen of Vibrio cholerae During the Course of Immunization of Rabbits.

Direct- and passive-agglutinating, complement-fixing, and bactericidal properties of gammaG and gammaM antibodies produced in rabbits inoculated with live Vibrio cholerae were determined at intervals over a period of 345 days. Although gammaM antibody titers increased more rapidly than gammaG during the initial stages of antibody production, the titers of gammaG and gammaM declined proportionally during a 3-month rest period and increased proportionally after a booster injection. The relative titers of gammaM as determined in the four serological procedures remained fairly constant throughout the period of observation. In contrast, early gammaG was less effective than late gammaG in vibriocidal, complement-fixing, and passive-hemagglutinating activity. At no stage of immunization was the agglutinating ability of gammaG affected by 2-mercaptoethanol, but its complement-dependent activity was markedly reduced, more so in early serum than in late. The heat lability of early gammaG approached that of gammaM, but gammaG became more resistant to heat in later stages of immunization.