Antibody responses and interferon titers in the respiratory tracts of mice after aerosolized exposure to influenza virus.

We studied the temporal appearance of immunoglobulins (immunoglobulins G1, G2, M, and A) and interferon in lung lavage fluids of mice after aerosol exposure to influenza virus in six animal groups in which mortality rates ranged from 0 to 24%. Immunoglobulin levels in the lung lavage fluids were markedly higher in mouse groups with higher mortality rates (16, 20, and 24%) than in those with low mortality rates (0, 2.5, and 7.5%). Analysis of serum albumin in the respiratory secretions as an index of edema indicated that increased immunoglobulin G levels during the early phase of infection were due to increased vascular permeability. The detection of virus-neutralizing antibodies and antibodies reactive with influenza virus antigens in the lavage fluids at 6 to 8 days postinfection suggested local immunoglobulin synthesis as a result of antigenic stimulation. Both systemic and local antibody productions contributed to immunoglobulin levels in the respiratory secretions after aerosolized influenza virus infection. Peak levels of interferon in the lavage fluids were reached before detection of significant levels of virus-neutralizing antibody in the serum or the lung lavage.