FACS staining profiles of Gr-1⁺ and Gr-1^–. Immunophenotyping using anti–Gr-1 and anti-CD11b antibodies on bone marrow cells from wild-type and leukemic mice. Based on the Gr-1 staining patterns, leukemias were classified as Gr-1⁺ or Gr-1^–. Both Gr-1⁺ and Gr-1^–leukemias displayed identical staining profiles for CD11b.