Differentiation of human monocytes into accessory cells at serum-free conditions

Human peripheral blood monocytes (HPBM) cultured in the absence of serum were found to convert into a state of high accessory function which was expressed by their ability to support lymphocyte proliferation. After a prolonged culture in serum-free media, the monocyte-derived cells were highly viable, increased in size, and had developed veils and dendritiform elongations. Paralleling the increase in accessory function, we found a decrease in the expression of markers typical of monocytes and macrophages (Mø), approaching the phenotype of lymphoid dendritic cells. We here define conditions for reproducibly generating these monocyte-derived accessory cells (m-AC) in various serum-free media, thus offering a novel differentiation model at highly defined culture conditions.