Pathogenesis of Trehalose Dimycolate-induced Interstitial Pneumonitis. IV. Evidence Against Roles for Immunoglobulins and the Complement System

We showed previously that trehalose dimycolate (TDM) in oil administered intraperitoneally into susceptible mice produced interstitial and hemorrhagic pneumonitis by the seventh day after injection and that mature T cells are necessary for the production of these lesions. TDM has been reported to activate complement and to be chemotactic for macrophages in vitro. Accordingly, we looked for involvement of humoral mechanisms in the pathogenesis of TDM-induced pneumonitis. Genetically C5-deficient B10D2/oSn mice developed pulmonary lesions just as well as C5-sufficient mice. No activation of C3 occurred in the plasma of TDM-treated mice as determined by crossed immunoelectrophoresis. Some splitting of C3 occurred in bronchoalveolar lavage fluids, but this was similar in control and experimental mice. By immunofluorescence microscopy, there was no deposition of C3 or immunoglobulins (Ig) along the alveolar membranes. These findings and our published data provide additional evidence that TDM-induced interstitial inflammation in mice is exclusively a T-lymphocyte-dependent process.