The epitope has not been fully characterized. Antigen distribution: Tissue sections: In frozen sections cells are stained in clearly defined areas in swine spleen. These districts are located in the red and white pulp. In addition, single cells in the red and white pulp are stained. Staining pattern in paraffin sections is strongly positive on follicular mantle B-lymphocytes whereas staining in germinal centre is weak. Specificity: Pig: Mx1 protein Other species: diffuse reaction in bovine spleen