Immunoglobulins are produced by cells of the B-lymphocyte lineage. Based on differences in the heavy chain, five immunoglobulin isotypes are known as IgA, IgG, IgM, IgD and IgE. IgA is the predominant immunoglobulin for mucosal immunity. It is found abundantly in mucosal tissues, such as gut, respiratory tract and urogenital tract. It is also found in saliva, tears and breast milk. An antibody to IgA is useful for the identification and classification of B-cell derived lymphomas and plasmacytomas.