Abstract
Human IgA occurs in two subclasses, IgA1 and IgA2, distinguished by antigenic, biochemical and biological properties (Mestecky & Russell 1986). The two subclasses are distributed in serum and external secretions, approximately 75% of serum IgA belongs to the IgA1 subclass, occurs predominantly in monomeric form, and originates from bone marrow. In contrast up to 60% of the IgA in external secretions belongs to the IgA2 subclass, is produced locally in secretory glands and tissues and is predominantly in polymeric form. The proportion of the polymeric and monomeric form of IgA is significantly increased in patients with cirrhosis (Kutteh et al., 1982; Newkirk et al., 1983; Kalsi, Delacroix & Hodgson, 1983). These observations suggest that the liver plays a role in the maintenance of normal levels of secretory and serum IgA. Human bile contains high levels of polymeric IgA,but the origin of this IgA is not clear. In this study we have compared the concentration of IgA antibody and its subclasses in 22 matched samples of human portal and peripheral venous blood and bile. Antibodies of each isotype to two oral bacteria were compared with those to two non-oral bacteria. In addition, the specific activity of antibodies in each fluid was calculated to determine if evidence for local production in bile could be found.
Published Version
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