Detection of Fas and FasL using flow cytometry. Various cells were stained for expression of Fas or FasL. A to G, Fas expression; H to J, FasL expression. Bold histograms represent cells incubated with FITC-conjugated secondary Abs only; broken histograms depict cells stained with anti-Fas or anti-FasL Abs + FITC-conjugated secondary Abs.