Dog immunoglobulins. II. The antibacterial properties of dog IgA, IgM and IgG antibodies to Vibrio cholerae.

Secretory IgA antibodies to Vibrio cholerae were purified from the parotid saliva and mammary secretions of locally and orally immunized dogs using gel filtration, ion-exchange chromatography and anti-immunoglobulin immuno-absorbents. IgM and IgG antibodies were isolated from serum by gel filtration and ion-exchange chromatography. IgA antibodies proved to have minimal, if any, activity in direct killing of bacteria in the presence of complement or in the promotion of phagocytosis. The minimal activity which IgA had in these assays could be accounted for by extremely small quantities of IgM antibody. The same IgA antibodies, mixed with the challenge innoculum of Vibrio cholerae and fed to infant mice, protected these mice as efficiently as IgG or IgM antibodies.