Effect of MoAb90 on T-cell subpopulations. CD45RA⁺ and CD45RO⁺ T-cell subpopulations were prepared as described in Materials and Methods. After 3 days of culture in the presence of immobilized-anti-CD3 (OKT3), viable cells from PBL or CD45RA and CD45RO T-cell subsets were treated with MoAb90 (▧, 10 μg/mL), YTH862 (, 10 μg/mL), or anti-Fas MoAb CH11 (, 1 μg/mL). The percentage of CD45RA, CD45RO, and double-positive CD45RA/RO-positive cells was assessed by fluorescence-activated cell sorting (FACS) analysis, and after 24 hours of incubation with antibodies, apoptosis was evaluated by fluorescence microscopy after Hoescht 33342 staining. Results are expressed as mean ± SD of three independent experiments.