IgAcontaining

IgA-containing is a term used to describe antibodies, immune complexes, or other immune entities in which immunoglobulin A (IgA) is a principal component. It can refer to IgA-bearing serum antibodies, secretory IgA in mucosal secretions, or immune complexes in which IgA is bound to antigen or other molecules.

Biology of IgA: IgA is produced mainly in mucosal-associated lymphoid tissue, exists as a monomer in serum and a dimer (secretory form) in mucosal secretions, joined by a J chain and, in secretions, by a secretory component. Two subclasses: IgA1 and IgA2.

Formation and function of IgA-containing immune complexes: IgA can form immune complexes with antigens; these IgA-containing immune complexes can bind Fc receptors FcαRI (CD89) on myeloid cells, triggering phagocytosis, respiratory burst, and release of inflammatory mediators. Unlike IgG, IgA activates complement poorly via the classical pathway, though some lectin pathway activation can occur.

Clinical relevance: IgA-containing immune complexes are implicated in certain diseases including IgA nephropathy (Berger disease) where IgA-containing complexes deposit in the glomerular mesangium, and IgA vasculitis (Henoch-Schönlein purpura) with systemic deposition. In mucosal diseases, secretory IgA can form immune complexes in the gut and airways.

Laboratory detection: Detection of IgA-containing antibodies or complexes uses immunoassays such as enzyme-linked immunosorbent assay (ELISA) with anti-IgA antibodies, nephelometry, immunofluorescence on tissue sections to detect IgA deposition, and precipitation assays.