Studies on IgA of the guinea-pig

Abstract

The secretory immunoglobulin of the guinea-pig, IgA, was antigenically unique when compared with the 7Sγ₁-, 7Sγ₂- and γM-globulins, although it did share Fab determinants in common with the 7Sγ₂ 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.