[Demonstration of secretory component in membrane structures of the human thymus]

A large amount of secretory component (Sc) was demonstrated in human thymus by the immunofluorescence technique. The component was found to be contained by the membranes permeating the parenhuyma and surrounding numerous tubular formations in the cortical layer of the organ under discussion. It is suggested that like other heteroorgan antigens, secretory component is involved in the formation of natural immunological tolerance, informing organ lymphocytes of the structures of the host own antigens. It is possible that in addition Sc promotes the differentiation of lymphocytes which repopulate to the lymphoid organs where serum IgA is synthesized and secretory IgA is formed.