Bone marrow–derived macrophages are CD44 v4 and v6 positive.

A 99% pure population of bone marrow–derived macrophages cultured as described in “Materials and methods” was double stained with anti-CD44 v4 and CD44 v6 antibodies. Cells (5 × 10⁵) were first incubated with the unlabeled primary antibody followed by incubation with PE-labeled secondary antibodies, and then the cells were treated with the FITC-labeled antibodies. Fluorescence was measured in a FACScan cytometer (Becton Dickinson). In the experiment shown, v6 antibodies were FITC labeled. In similar experiments, FITC-labeled v4 antibodies gave the same result (not shown).