Effect of G-CSF on production of IL-12 by DCs from donors.

Expression of the gene for the inducible IL-12p40 subunit and production of the bioactive IL-12p70 protein were determined in DCs differentiated from monocytes from healthy donors. Top panels (in vivo) show results when monocytes from G-CSF–treated donors were subjected to standard DC differentiation conditions and activated with CD40 ligand. Unlike control DCs (G-CSF−), DCs differentiated from monocytes treated in vivo with G-CSF– did not express the IL-12p40 gene (shown is one representative RT-PCR assay, left side). Bottom panels (in vitro) show results when normal monocytes were incubated in the presence of G-CSF for 24 hours, washed, and subjected to standard DC differentiation conditions. DCs differentiated from G-CSF–treated monocytes did not express the IL-12p40 gene (left side). ELISA analyses (right side of each panel) confirmed that IL-12p40 gene expression (mRNA+) correlated with actual production of bioactive IL-12. Values are mean ± SE levels of IL-12 protein production by all IL-12p40 mRNA⁺ samples in the in vivo (top) and in vitro (bottom) G-CSF treatment protocols. C indicates β-actin–specific or IL-12p40–specific control; and N, no DNA added to the amplification mix during PCR.