Induction of c-fos in mouse bone marrow macrophages: a direct method for assessing bone marrow cell activation

Intravenous LPS was used to induce bone marrow cell activation in c-fos/lacZ transgenic mice. Activated bone marrow cells were identified by staining with X-gal and cell lineage was determined using specific monoclonal antibodies. Four hours after intravenous injection of 100 micrograms LPS, 2.8 +/- 0.2% (28/1000) of total bone marrow cells was X-gal positive as compared to 0 +/- 0% (0/1000) of cells from untreated animals. CD8a, CD4 and CD45R antigens were not expressed on X-gal positive cells suggesting they were not from the T or B lymphocyte lineage. In contrast, Ly-6c, CD44 and Gr-1 antigens were expressed on 51 +/- 6%, 85 +/- 9% and 37 +/- 5% of X-gal positive cells, indicating that X-gal positive cells were from macrophage or granulocyte lineages. The presence of non-specific esterase and the lack of peroxidase activity in X-gal positive cells was used to conclude that X-gal positive cells were of macrophage lineage.