[Demonstration of IgM antibodies in influenza virus infections]

Forty-Four sera of patients with confirmed influenza-A infection were titrated in parallel with and without 2-mercaptoethanic treatment against influenza-A by means of passive haemagglutination. Reduction of titre by at least two levels was detectable in 21 cases. Gradient centrifugation was additionally undertaken of 23 patient sera and three serum samples obtained from intact probands who had produced a titre against influenza-A in passive haemagglutination. Antibody against influenza-A was present in both the IgM and IgG fractions of the patients' serum samples. Yet, in the three control sera of intact probands antibody against influenza-A was recordable only from the IgG fraction. IgM antibody could not be detected by 2-mercaptoethanoic treatment alone unless the 7s-antibody portion in a given serum sample was smaller than the 19s-antibody portion.