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viral antigen that remains in solution after the particles of virus have been removed by means of centrifugation; in the case of the influenza viruses, it is the internal helical structure, free of the external envelope.
Synonym(s): S antigen (1)
An antigen dissolved in a liquid. A soluble antigen is recognized by B lymphocytes but cannot be detected by T lymphocytes until it has been processed by an antigen-presenting cell. See: T cell.
See also: antigen