Circulating antibodies and respiratory virus infections.

Most respiratory viruses infect only the respiratory mucosa and mainly the surface epithelium, and it is therefore plausible that antibody within the circulation is unable to influence them, either by preventing infection or by terminating it once it has started. However there is experimental and observational evidence that some infections are prevented by circulating antibody. This may be because circulating immunoglobulins are released onto the surface possibly because of virus cytopathic effects or hypersensitivity to a viral antigen.