Immunofluorescence analysis of IL-7 binding to stromal cell plasma membrane HS. (A) BMS2 stromal cells were stained with an antibody (SB/14) to the IL-7 receptor  chain or rat IgG_2a followed by goat anti-rat Ig-FITC; the binding profiles directly overlap. (B) Mock- (control) or heparitinase-digested (+ h’ase) BMS2 cells were stained with biotinylated IL-7 or the negative control reagent (STI) as described in the legend to Fig 3. Control BMS2 cells displayed a bimodal profile (rightmost peaks). Binding of biotinylated IL-7 was readily blocked using a neutralizing antibody to IL-7 and efficacy of the digestion procedure was confirmed using the 10E4 and 3G10 MoAbs (data not shown).