BLyS binding in monocytes. (A) Freshly isolated monocytes were incubated without (open curve) or with (gray shaded curve) flag-tagged BLyS, and binding was visualized by flow cytometry using a biotinylated anti-flag antibody and PE-streptavidin. (B) Freshly isolated monocytes were incubated with _LBLyS (Exp 1) or _SBLyS (Exp 2), or without BLyS (Nil) before washing, cell lysis, and analysis of BLyS binding by Western blotting