Studies of porcine secretory IgA and its component chains in relation to intestinal absorption of colostral immunoglobulins by the neonatal pig.

Porcine secretory component was identified after reductive dissociation of secretory IgA and isolated in the free form from sow milk. Electrophoretically fast polypeptide chains were detected in the light chain fraction of reduced and alkylated porcine secretory IgA. These probably relate to J chain and were immunologically and electrophoretically distinct from secretory component. J chains were not present in the light chain fractions of reduced and alkylated porcine 7S IgG and 6.4S IgA. Porcine colostral IgA occurs in a wide range of molecular sizes and IgA lacking secretory component having S 6.4 and 9.3 was isolated from colostrum and serum of suckling piglets. A haemagglutination inhibition assay for 10.6S secretory IgA using specific rabbit anti porcine secretory component demonstrated that only a very small proportion of the IgA derived from colostrum is 10.6S IgA with secretory component.