Studies of peritoneal macrophage function in murine systemic lupus erythematosus. 2. Nature of elevated resident peritoneal cells in NZB and (NZB x NZW)F1 mice

The numbers of resident peritoneal cells recovered from NZB and (NZB X NZW)F1 hybrid mice, which develop systemic lupus erythematosus (SLE), increased strikingly with age as compared with cells recovered from normal mice. The rise paralleled the onset of anti-DNA antibodies, occurring earlier in females than in males. The increased number of cells was due to an accumulation of medium-sized cells with an indeterminate appearance, but with the functional characteristics and cell markers typical of a macrophage. The unusual cells were esterase, F4/80 and Mac-1 positive, peroxidase, and Alcian blue negative, and were shown on sedimentation velocity separation to be phagocytic for EA and C3 (serum-treated) zymosan; 47-48% of peritoneal cells were Ia positive.