STUDIES ON PRIMARY ATYPICAL PNEUMONIA : III. A FACTOR IN NORMAL SERUM WHICH ENHANCES THE REACTION BETWEEN PAP VIRUS AND CONVALESCENT SERUM

A factor present in fresh normal human or guinea pig serum enhances the primary atypical pneumonia (PAP) antibody titers in serological reaction with its homologous virus as tested by indirect fluorescent antibody staining. This factor is not properdin. It has many properties similar to complement but may not be identical with complement. The addition of this enhancement factor to human sera convalescent from primary atypical pneumonia has made the serological test more sensitive without affecting its specificity.