Undetectable IgE as a Sentinel Biomarker for Humoral Immunodeficiency

Inclusion Criteria: * Age 18-80 * Willingness and ability to comply with scheduled visits and study procedures * Undetectable serum IgE (defined as \>2 IU/mL or the lower threshold of detection) * Normal or high serum immunoglobulins (within or above laboratory reference range for IgG, IgA, and IgM) * patients previously seen at the University of Virginia Asthma, Allergy, and Immunology clinics where undetectable serum IgE was noted * Control subjects must have participated in study IRB#14457 (only applicable for healthy controls in epsilon germline transcript portion of the study) Exclusion Criteria: * The following vulnerable populations will be excluded: pregnant women, fetuses, neonates, children, prisoners, cognitively impaired, educational or economically disadvantaged, non-English speaking subjects * Known personal history of immunodeficiency * Known personal history of recurrent infections * Low serum immunoglobulins (below the laboratory reference range for IgG, IgA, or IgM) * Recent or current treatment with systemic immunosuppression within the past 30 days