Survival-promoting activity in size-fractionated ECCM.
ECCM was concentrated with an Amicon filtration device and then passed through a Sephacryl S-200 gel filtration column equilibrated with PBS. Each fraction was assayed at dilution 1:2 on B-CLL cells to determine their antiapoptotic activity. IL-6 content (■) was measured as described in “Materials and methods.” The Mr standards are indicated by arrows; ●, A280; ×, annexin-V. A representative experiment of 3 similar elution profiles is shown. The inset shows the antiapoptotic activity of monomeric and dimeric forms of endothelial IL-6. B-CLL cells were incubated with various concentrations of IL-6D (■) or IL-6M (●). Percentages of apoptotic cells were measured in a 48-hour assay. These results were confirmed in 2 additional experiments. Results are expressed relative to the percentage of apoptosis observed in the CM.