ABSTRACT
This chapter shows that patients defective secretory immunity due to a lack of secretory. Secretory immunoglobulin A (IgA) have a particularly permeable gastrointestinal tract which allows the absorption of antigenically intact dietary macromolecules. In health, the mucous membranes of the mature gut are relatively impermeable to large dietary molecules owing to the intrinsic structure of this barrier and the mucosal immune system. The mucosal epithelium consists of several different types of cells—the border cells and goblet cells are the most common. Since at least some anti-idiotypes made by the IgA-deficient individual are directed at the binding site of the primary antibody, it seems more likely that casein antigen and the anti-idiotype bind alternatively to the primary antibody, depending upon the serum concentration of the relative antigen at each point in time. However, for still unknown reasons, the amounts of protein in the sera of hypogammaglobulinemic patients are closely associated with the presence of splenomegaly and/or lymphadenopathy.
