Expression of CD11b antigen in wild-type HL-60, parental HL-60R, HL-60R/neo, and HL-60R/196Rz cells by fluorescence-activated cell sorting (FACS) analysis. Cells were cultured with 10^-7 mol/L of either all-trans RA or 9-cisRA for 4 days. Cells were incubated for 30 minutes with human AB serum to block Fc receptors, and then stained with PE-conjugated mouse antihuman CD11b antibody. Control studies were performed with control mouse IgG isotype antibody.