Binding of SSL5 to leukocytes. Two-color flow cytometry was used to analyze SSL5 binding to different leukocyte subpopulations. (A) Leukocytes were incubated with 10 μg/mL SSL5-FITC for 30 minutes on ice. To differentiate for specific leukocyte subpopulations, monocytes, T lymphocytes, and B lymphocytes were concurrently stained with PE-conjugated antibodies directed against CD14, CD4 or CD8, and CD19, respectively. NK cells were first negatively selected for binding of anti–CD3-Cy and then positively selected for binding anti–CD16-PE and anti–CD56-PE. Neutrophils were selected only by gating. (B) Binding of a concentration range of SSL5-FITC (0.3-10 μg/mL) to the different leukocyte subpopulations. The data represent mean fluorescence of detected SSL5-FITC and are representative of 3 independent experiments.