Fractionation of untreated and inflammatory murine peritoneal macrophages on discontinuous Percoll density gradients.

Peritoneal cells from C57/BL/6J mice untreated or injected with saline, proteose-peptone or Corynebacterium parvum intraperitoneally or Sauton medium or BCG intravenously were fractionated on discontinuous Percoll gradients. Six subsets of macrophages were obtained in all the groups. Injection of BCG and proteose-peptone increased the percentage of heavy density macrophages whereas C. parvum caused an increase in macrophages in the lighter density fractions. The macrophages in all the subsets were tested for their ability to kill L929 target cells and cytochemically for expression of beta-galactosidase. The highest degree of cytotoxicity was found in the higher density subsets, although the other subsets in the C. parvum group were also cytotoxic. There was a marked reduction in beta-galactosidase in macrophages obtained after injection of C. parvum and to a varying degree after injection of BCG, proteose-peptone or saline. Cells which were devoid of enzyme were evenly distributed throughout the subsets. These studies indicate that a certain degree of separation of cytotoxic macrophages can be achieved by density centrifugation, but not of cells containing different amounts of beta-galactosidase.