Studies on IgA of the guinea-pig.

The secretory immunoglobulin of the guinea-pig, IgA, was antigenically unique when compared with the 7Sγ-, 7Sγ- and γM-globulins, although it did share Fab determinants in common with the 7Sγ globulin. Specific antigen binding capacity was detected in serum IgA after sequential oral and parenteral sensitization with purified protein antigens. IgA was prominent in saliva and succus entericus; in colostrum its concentration was 4–8 times that in normal serum. IgA in serum and secretory fluids sedimented at similar rates (≃12S), although colostral IgA contained an additional ≃16S population. Serum and secretory IgA appeared antigenically identical, however, serum IgA was especially sensitive to mild reductive procedures and became ≃7S after treatment. Serum IgA migrated as a β-protein on electrophoresis and was faster than IgA of colostrum. Antisera to IgA were produced by a procedure which involved simple precipitation of secretory IgA with an antiserum containing antibodies to common determinants of guinea-pig Ig.