Fas expression (flow cytometry with anti-Fas MoAbs directly conjugated to R-PE) in 3DO (A) and HDK-1 (B) cells after 20 hours of in vitro culture in 96-well plates with medium alone (control) or coated with anti-CD3 MoAbs (1 μg/well) and /or anti-CD2 MoAbs (5 or 1 μg/well). The number represents the value of the histogram median calculated by Lysis II. Fluorescence intensity versus cell number is shown.