Enhanced in vitro phagocytic power of macrophages from PPD-stimulated skin sites in human subjects hypersensitive to PPD.

By a quantitative Rebuck's skin-window technique human macrophages were collected from individuals either unreactive or hypersensitive to PPD, the latter having recovered from tuberculous infection. In vitro testing of macrophages with a strain of Paracolonbacter aerogenoides proved that cells from hypersensitive convalescents were provided with increased pagocytic and bactericidal activities. An even higher degree of macrophage activation was attained when cells from hypersensitive individuals had previously been stimulated in vitro with PPD. Changes of macrophage functions such as those mentioned above might well result from the action on macrophages of lympho-kine-like agents released by sensitized lymphocytes coming in contact with PPD.