BINDING OF SERUM AUTOANTIBODIES TO SIALIDASE-TREATED TRACHEAL EPITHELIAL-CELLS - DETERMINATION OF AUTOANTIBODIES ISOTYPES IN NORMAL AND INFLUENZA-VIRUS INFECTED GUINEA-PIG SERA

Cultured epithelial cells isolated from guinea pig trachea were treate d with Vibrio cholerae sialidase. The treatment was not cytotoxic and resulted in membrane desialylation as assessed by measurement of siali c acids released, along with an increased fixation of the galactose-sp ecific lectin peanut agglutinin. After incubation in serum from normal guinea pigs, membrane-bound immunoglobulins were detected using perox idase-labelled antibodies. Sialidase-treated cells bound significantly more IgM than controls (P < 0.0005), whereas binding of IgG was not s ignificantly different between treated and untreated cells (0.1 < P < 0.375); IgA were never detected. In influenza-infected guinea-pigs, as assessed by reactivity with peanut agglutinin, the tracheal and lung epithelium, as well as alveolar cells were hyposialylated. In these an imals, the level of serum IgG autoantibodies capable to bind sialidase treated cultured cells increased, while the level of IgM autoantibodi es did not change. These autoantibodies may participate in cellular dy sfunctions and modified bronchoreactivity that occur during infection of the respiratory tract by sialidase-producing microorganisms, either through activation of the complement system, or subsequently to their reaction with cells expressing membrane complement and/or Fc receptor s.