Secretion of IgA into 'antigen-free' isografts of mouse small intestine.

The immunoglobulins secreted into "antigen-free" isografts of mouse small intestine have been measured by single radial immunodiffusion and immunoelectrophoresis of tissue extracts. IgA was detected in high concentration, and small amounts of IgG1 and IgG2 were also present. The IgA content of material within the graft lumen was considerably higher than the IgA content of the graft wall, indicating that IgA had been secreted and stored. Graft IgA increased with time after implantation, and no differences in immunoglobulin contents were found when grafts in thymus-deprived and in normal mice were compared. A group of host mice had been immunized with BSA and had high titres of circulating antibody to BSA; anti-BSA was not detected in the grafts implanted in these mice. However, graft extracts had moderately high titres of bacterial agglutinins when tested against a panel of commensal gut bacteria. These results indicate that secretion of IgA into a segment of small intestine is not dependent upon the presence of antigens within its lumen; however, the immunoglobulins secreted may have antibody activity against antigens present in small intestine elsewhere in the animal.