The Isolation and Biologic Activities of Purified Secretory IgA and IgG Anti-Salmonella Typhimurium “O” Antibodies from Rabbit Intestinal Fluid and Colostrum

Direct contact of external secretory tissue with living, but not with dead, Salmonella typhimurium stimulated formation of high concentrations of anti-“O” antibodies in the small intestinal fluid and colostrum. Purified IgG and IgA anti-S. typhimurium “O” antibodies were isolated from these fluids and their activities measured on a molar basis. Serum and exocrine IgG molecules had identical complement-dependent bactericidal, opsonization and PCA reactions. Exocrine IgA antibodies showed little or no activity in these biologic assays but did exert a similar suppressive effect upon antibody formation after intravenous injection or oral administration, as did exocrine IgG antibodies. Both IgA and IgG molecules had similar specific agglutination activities.