Biological activity of IL-2 and GM-CSF in DCH and variants. (A) The biological activity of IL-2 was measured by cellular proliferation of the IL-2-dependent murine T cell line CTLL-2. CTLL-2 cells were incubated with various concentrations of free recombinant human IL-2 (rhIL-2) and equivalent amounts of IL-2 in purified DCH proteins. (B) The biological activity of GM-CSF was measured by cellular proliferation of the GM-CSF-dependent human erythroleukemia cell line TF-1. TF-1 cells were incubated with various concentrations of free recombinant human GM-CSF (rhGM-CSF) and equivalent amounts of GM-CSF in purified DCH molecules. The number of viable cells was determined in a WST-1 colorimetric assay. All results are expressed as mean absorbance A₄₅₀-A₆₂₀ of triplicate determinations.