Secretory Immunoglobulin a (Siga) in Middle Ear Effusions

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Abstract
Immunochemical studies of secretory immunoglobulin A (SIgA) in middle ear effusions were attempted for the purpose of investigating the existence of the local immunologic defense mechanism and the local protein synthesis in the middle ear. SIgA was isolated from normal human parotid secretions by means of DEAE-cellulose column chromatography and G-200 Sephadex gel filtration. Antiserum against SIgA was made by immunizing a rabbit with the SIgA isolated from the parotid secretions. Antisecretory piece antiserum was made by absorbing the anti-SIgA antiserum with pooled normal human sera. Immunodiffusion analysis of SIgA was performed on 160 specimens of middle ear effusion from patients with otitis media with effusion. Seventy-five of 160 (46.9%) specimens were found to have SIgA. In the serous category 5 of 41 (12.2%) acute cases were positive while 24 of 59 (40.7%) chronic cases were positive. One of 2 acute cases of the seropurulent effusions showed the positive reaction and 2 of 3 cases of the purulent type were positive. In the mucopurulent type 2 of 4 acute cases were positive and all 3 chronic cases were positive. In the mucoid type 9 of 14 (64%) acute cases gave a positive precipitation line while 29 of 33 (87.9%) chronic cases gave the positive reaction. The appearance of precipitation line developed with effusions varies from very faint to distinct. However, as a rule the line of the mucoid, mucopurulent and purulent effusions was strong. Since SIgA is the predominant immunoglobulin in external secretions but is not present or is at very low concentration in normal sera, findings of this study suggested that the middle ear lining membrane possesses the secretory function similar to the epithelium of other external secretory tissues, and suggested the hypothesis that the middle ear epithelium shares the local immunologic defense system as that of respiratory epithelium.

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