The predominant immunoglobulin found in exocrine secretions of humans and most other mammals is secretory IgA, a polymeric form of IgA containing an additional glycoprotein chain designated "secretory component." In this article recommended abbreviations are proposed for the following forms of human IgA and other proteins of related interest: secretory IgA, secretory IgM, secretory component, polymeric immunoglobulin receptor, polymeric IgA, monomeric IgA, IgA subclass 1, IgA subclass 2, A2 allotype marker 1, and A2 allotype marker 2