IgA antibodies play a central role in defence against pathogens by preventing adhesion penetration. Reduced levels can be due to a congenital deficiency, to certain disorders (IgG myeloma and lymphoma) or in response to certain drugs. Very high levels of monoclonal IgA are associated with IgA myeloma, benign blood globulin disorders in elderly patients and certain severe infectious diseases. IgA has a mol wt of 160 kDa.