Evaluation of LGL apoptosis and P-STAT3 level in the presence of neutralizing antibodies against IL-6 and IL-6Rα. Apoptosis was measured after 1, 2, 4, and 7 days of culture in RPMI 0.5% FCS by Annexin V/PI. Staining with anti-CD57-FITC was used to identify leukemic LGLs from PBMCs. (A) Purified LGL apoptosis was analyzed in cells cultured alone or cells cultured with autologous PBMCs, IL-6, or autologous plasma 10%. (B) LGL apoptosis time course and (C) western blot analysis of P-STAT3 and STAT3 in PBMC at 4 hours of culture (2 representative patients) with control IgG1, anti-IL6, and anti-IL-6Rα antibodies. β-Actin served as a loading control. (D) LGL apoptosis in culture alone and with autologous plasma in the presence of an isotype control antibody, anti-IL6 antibody, and anti-IL-6Rα antibody. The apoptosis histograms show the mean results (± SE) from 4 individual experiments.