Molecular Cloning of a Novel Protein, Human Mast Cell Surface Antigen and its Clinical Applications

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Mast cells are pivotal effector cells in allergic and inflammatory reactions. Mast cell activation can lead to bronchoconstriction, increase in vascular permeability, and other effects in inflammation, immunity and tissue remodeling. However, little is known about the cell surface markers specific to mast cell activation. In the search for molecules expressed in mast cell surface, we -identified a novel protein, named mast cell surface antigen (MASA)-1 and its complementary DNA by immunoscreening. MASA-1 mRNA was established to comprise 2571 bp with an ORF of 2358 bp, predicting a protein of 786 amino acids with a molecular weight of 86 kDa. MASA-1 was found to be expressed in mast cells in bronchoalveolar lavage fluid from patients with subacute or chronic inflammatory diseases such as bronchiolitis obliterans organizing pneumonia (BOOP), sarcoidosis and idiopathic interstitial pneumonia, while it was not expressed in mast cells in normal human tissue examined, such as the lung, nasal mucosa, skin, gastrointestinal tract. MASA-1 was expressed in mast cells in the lesional tissue of BOOP and idiopathic interstitial pneumonia. MASA-1 was expressed in mast cells cultured from cord blood mononuclear cells and mastocytoma cell lines, HMC-1 and RBL-2H3 cells by Western blotting and flow cytometry, though MASA-1 was not expressed in human and rat leukocytes and other cell lines tested. Stem cell factor or transforming growth factor-β1, -β2,, and -β3 up-regulated MASA-1 expression in HMC-1 cells in a dose-dependent manner. These results indicate that inflammatory cytokines induce MASA-1 expression and thus MASA-1 will serve as a novel marker for mast cell activation. -