For all leukemic specimens analyzed, KG1a cell HCLL activity was assessed in parallel to serve as a comparative control. Cytospins of buffer-, OSGP-, mocarhagin- or neuraminidase (Newcastle)-treated blasts or KG1a cells were prepared and underwent Stamper-Woodruff assay as described in “Materials and methods.” Lymphocytes adherent to leukemic cell monolayers were counted by light microscopy using an ocular grid under 100 × magnification (3 fields per slide, 3 slides per experiment, 3 separate experiments). L-selectin dependence lymphocyte adhesion was confirmed in every experiment as described in “Materials and methods.” Note that L-selectin ligand activity in all treated groups was resistant to OSGP and mocarhagin, and sensitive to neuraminidase.

All leukemia specimens showed >80% expression of CD34 and of PSGL-1 except as where indicated by footnote symbols

Results from Stamper-Woodruff assay are presented as percentage of cytocentrifuged cells with adherent lymphocytes: −, 0 to 10%, +, 11 to 35%, ++, 36 to 60%, +++, 61 to 85%, and ++++, 86 to 100%.

Two different specimens of leukemias with these subtypes were evaluated.

This leukemia was negative for all histochemical markers and displayed both myeloid (CD13⁺/CD33⁺) and B-lymphoid (CD10⁺/CD19⁺/TdT⁺) cell markers; PSGL-1 expression was low (18% PSGL-1⁺, see below for staining profiles).

PSGL-1 expression was low (14% PSGL-1⁺ blasts).

CD34 expression was absent (<5%) on leukemic cells from one of the 2 patients with M4 and one of the 2 patients with M5 as determined by flow cytometry.

nd, not determined