Expression of cytotoxic T-lymphocyte antigen 2 alpha in mouse bronchiolar epithelial cells: anatomical and functional implications

The lung is one of the major sites of cathepsins (B, H, and L) expression where they are involved in several functions including degradation of extracellular matrix proteins, remodelling of the lung tissue and processing of the invariant chain of the MHC class II complex. Under pathological conditions, cathepsins have been observed in inflammation, tumour progression and metastasis. The enzymatic activity of cathepsins is regulated by changes in pH and their interaction with inhibitors. One of the potent and specific inhibitors of cathepsin L is the Cytotoxic T-lymphocyte antigen-2α (CTLA-2α) which was originally expressed in mouse activated T-cells and mast cells. However, the cellular localization and distribution pattern of CTLA-2α in the lung is not known. In this study, CTLA-2α expression in the lung was evaluated by immunofluorescence. Strong immunoreactivity was specifically detected in the bronchiolar epithelial cells of primary, secondary and terminal segments; moderate in the lymphoid nodules and scanty in the lung parenchyma. The distribution pattern implicates an important role of this inhibitor protein in relation to matrix remodelling, immune response and their relationship to lung development and diseases