Ig, immune gamma globulin, immune globulin, immune serum globulin, immunoglobulin - a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response

reagin - an immunoglobulin E that is formed as an antibody against allergens (such as pollen); attaches to cell membranes causing the release of histamine and other substances responsible for the local inflammation characteristic of an allergy