CD163 antigen is a type I membrane protein also known as M130 antigen, Ber-Mac3, Ki-M8 or SM4. CD163 is restricted in its expression to the monocytic/macrophage lineage. It is present on all circulating monocytes and most tissue macrophages except those found in the mantle zone and germinal centers of lymphoid follicles, interdigitating reticulum cells and Langerhan’s cells.