Immunoglobulin (Ig): These are the protein molecules also called antibodies. These act against the foreign antigens entering the body, and neutralizes them.An antibody has a Y-shaped structure. Each antibody molecule consists of four polypeptide chains, two are long called heavy (H) chains while the other two are short called light (L) chains. Hence, an antibody is represented as H2L2.Antibodies can be classified into five types IgA, IgM, IgE, IgG & IgD.Explanation:IgE: IgE is produced in plasma cells. It is primarily found in mammals.It constitutes 0.05% of the total Ig in serum. It has a molecular weight of 200,000 daltonsIt mediates hypersensitive or allergic reactions like dust allergy, pollen allergy, etc that cause symptoms like sneezing, coughing, itchy eyes, etc.When the body encounters an IgE-specific antigen, the IgE gets attached to the mast cells which causes a release of powerful chemical mediators like histamine from the mast cells and an allergic reaction is initiated.Additional InformationIgE antibodies:It is involved in triggering the immune system to attack the parasite that infects the cells.It is also involved in triggering allergic reactions.IgG antibodies:Up to 75% of antibodies in the blood are of this type.Its main function is to provide protection against reinfection with microorganisms that have previously encountered the immune system.IgM antibodies:It is involved in the initial immune response to an infection and is one of the first antibody isotypes produced by B lymphocytes.