R macrophages which was derived from brochoalveolar lavage (BAL) obtained from MS-/- mice [31]. Immortalization was conducted by infection of the primary AMs from MS/- mice with a retrovirus J2. The immortalized AMs were cloned by limiting dilution method. Three of the clones, designated as ZK-1, ZK-2 and ZK-6 were chosen for further characterization of macrophage phenotype and phagocytic function