Experimental Pleural Effusion as a Manifestation of Delayed Hypersensitivity to Tuberculin PPD

Summary Evidence is presented that pleural effusions in guinea pigs may be induced by hypersensitivity to PPD in the absence of infection with tuberculous organisms. Transfer of this reaction with cells from immunized animals indicates a predominant role of the delayed type of hypersensitivity, and documents an additional physiologic effect of this form of hypersensitivity reaction in vivo. Differences found in the protein concentrations of these effusions are compatible with differences in control of macromolecular movement in effusions induced by this hypersensitivity reaction, when compared with effusions resulting from nonspecific chemical injury. Studies utilizing in vitro incubations of lungs from sensitized donors indicate a role of soluble mediators released during the hypersensitivity reaction in the induction of pleural effusions, and thus suggest the importance of such mediators in in vivo manifestations of delayed hypersensitivity.