Localization of b markers, alpha-chain and SC of SIgA in epithelial cells lining Lieberkühn crypts.

Abstract

Local synthesis of immunoglobulins (Igs) has been demonstrated in tissues surrounding epithelial cell layers engaged in secretion, such as in salivary glands, gastrointestinal tract, mammary glands and respiratory tract (1–4). Several theories have been put forth (4–6) to explain the passage of Igs, particularly secretory IgA (sIgA), from the plasma cells in the sub-epithelial spaces to the lumen of the various glands and organs. These have also been necessarily concerned with the assembly of the sIgA 11S dimer and its association with secretory component (SC), because the latter component can be localized in epithelial cells (1, 7) rather than in the plasma cells which synthesize the α and light chains of IgA. As yet, the route of the IgA molecule from the plasma cells to the lumen of various secretory glands has not been clearly delineated. However, the presence of IgA in between and/or at the apex both of the absorptive and glandular epithelial cells of the intestine has been described (4, 8, 9).