GM-CSF and IL-4 in combination abolish osteoclastogenesis while inducing formation of immature DCs. Monocytes were cultured in the presence of M-CSF and sRANKL (top panels). GM-CSF and IL-4 in combination were added to the monocytic cultures together with M-CSF and sRANKL (bottom panels) with replacement of half of the medium and addition of the cytokines every 3 days. The cells were stained for TRAP at day 14 (left panels), and cell surface CD1a and CD14 expression was analyzed at day 5 by flow cytometry.