IGA SYSTEM .2. CLINICAL SIGNIFICANCE OF IGA DEFICIENCY - STUDIES IN PATIENTS WITH AGAMMAGLOBULINEMIA AND ATAXIA-TELANGIETASIA

IgA is absent from serum and saliva at birth, and gradually reaches adult levels by the time of puberty. In a study of eighteen agammaglobulinemic and two hypoammaglobulinemic patients, nineteen were found to have manifestations of chronic respiratory tract infections in spite of immunoglobulin replacement therapy; the twentieth patient, who was well, was the only one who had significant levels of IgA in his saliva. Twenty-two patients with ataxia-telangiectasia also were studied. Eight had no detectable IgA in their saliva, and they showed significantly more severe sinopulmonary disease than did those who had IgA in their saliva. The remaining fourteen patients with ataxia-telangiectasia had a mean level of IgA in saliva lower than normal, and a mean serum IgA which showed a trend toward low levels. No correlation between the severity of the respiratory tract infections in these fourteen patients and the IgA levels in either serum or saliva was observed. Transport piece, the secretion-specific part of the IgA molecule, was found in the saliva of every person studied, regardless of the presence or absence of IgA in serum or saliva. We interpret these findings as support for two hypotheses: (1) There is a local antibody system involving IgA for the protection of the mucous surfaces, the absence of which produces susceptibility to infection of those surfaces, most especially of the respiratory tract. (2) The transport piece and the IgA molecule are synthesized separately although the two are specifically bonded when found in the secretions bathing the body surfaces. © 1968.