Description: The monoclonal antibody IgE21 recognizes the immunoglobulin E class of antibodies. The natural levels of IgE in the serum are quite low, comprising only a small portion of the total immunoglobulin. IgE plays a role in allergy responses by binding to mast cells and basophils through the Fcε receptor I which results in the release of histamine and other molecules. The IgE is produced by terminally differentiated plasma B cells and basophils. Like all immunoglobulins, IgE is expressed as a soluble molecule as well as a membrane bound form. IgE21 recognizes both forms.