Isolation of the secretory component of immunoglobulin A and production of a specific antiserum

This study was the initial step in a long range investigation of the local immune system of the urinary tract. The presence of secretory immunoglobulin A in external secretions exercises broad spectrum antimicrobial activity; the high incidence of chronic urinary tract infections, particularly among females, may result from a deficit of this system. As degraded serum immunoglobulin A is excreted in the urine, the fragmented alpha chains would react with the available antiserum to whole secretory immunoglobulin A molecule, and alter the levels of secretory immunoglobulin A assayed. It was therefore necessary to develop a method of determining levels of both secretory immunoglobulin A and secretory component. The secretory component was isolated and partially purified from pooled human colostrum. The major and overwhelming contaminant was lactoferrin. Antisera to these proteins were then developed in rabbits. An attempt was made to separate the rabbit antibodies to the secretory component and the antibodies to the other proteins which were mainly lactoferrin. A double diffusion in gel using the rabbit antisera and tlie antigen to develop antigen-antibody complexes which were then reinjected into rabbits was used. Despite this purification attemp, the final antisera contained a greater quantity of antibodies to the lactoferrin than ti secretory component.