Chronic sinusitis, steroid-dependent asthma, and IgG subclass and selective antibody deficiencies.

In the past 20 years considerable progress has been made in understanding the ways in which subtle immunologic defects can adversely affect health. Immunoglobulin G subclass deficiencies have been identified and are related to an increased susceptibility to respiratory tract infections in certain patients. To assess the immunocompetence of such patients, the quantity and quality of their antibody response must be evaluated. Immunologic evaluation is best performed by measuring selective antibodies before and after a specific challenge. Patients with mild immunodeficiency may benefit from prophylactic antibiotic therapy; those with profound immunodeficiency require antibody replacement therapy.