Differentiation of CD34⁺ cells upon culture with allogeneic T cells is mediated by endogenous GM-CSF and TNFα. Purified CD34⁺ cells were cultured with irradiated allogeneic T cells alone (control) or in the presence of anti-GM-CSF (anti-GM-CSF), anti-TNFα (anti-TNFα) mAb, or both (anti-GM-CSF anti-TNFα), then analyzed by flow cytometry for the expression of CD86 and CD11c. Markers were set in each histogram based upon isotype controls in order to calculate the percentage of positive cells.