CD44 is required for HK-induced protection of CLL B cells.

CLL B cells were cultured for 24 hours alone or together with HK cells in the presence or absence of 10 μg/mL CD44, CD40, ICAM-1, or β1-integrin neutralizing antibodies. CLL B cells were recovered from cultures, and the percentage of apoptotic cells was determined by annexin V–FITC/PI double staining by means of flow cytometric analysis (n = 7). Simultaneously, protein-containing lysates were prepared, and 12.5 μg per lane protein from each lysate was analyzed by SDS-PAGE/immunoblot assay with the use of antibodies specific for Mcl-1 or β-actin. (One representative experiment of a total of 3 is presented.)