T cell localization in rabbit models of acute and chronic experimental hypersensitivity pneumonitis.

Cell-mediated hypersensitivity has been increasingly implicated in immunologic diseases of the lung, including hypersensitivity pneumonitis (HSP) (extrinsic allergic alveolitis). We used a T cell-specific monoclonal antibody (L11/135) to localize T cells in the parenchyma and bronchus-associated lymphoid tissue of ethanol-fixed, paraffin-embedded lung sections in rabbit models of experimental HSP to define further their possible role in pathogenesis. T cells appeared within 4 hours in early lesions of rabbit models of acute HSP and heavily infiltrated alveolitis lesions at 8 and 24 hours after aerosol challenge. T cells were also present in lesions of rabbit models with chronic alveolitis and occurred peripherally in granulomas. Variable aggregate and follicular forms of bronchus-associated lymphoid tissue rich in T cells occurred in both experimental and control animals. Our findings document early and continuing presence of T cells in lesions in rabbit models of experimental HSP.