Potent allo-antigen (allo-Ag)-presenting function of CD34-derived APCs induced by allogeneic T cells. Purified CD34⁺ cells, either freshly isolated (□), after culture with irradiated allogeneic T cells for 6 days (Irrad Allo-T cells, ▪), or with irradiated allogeneic T cells and anti-GM-CSF plus anti-TNFα blocking antibodies (blocking MAbs, ▦), were irradiated and mixed with blood T-cell responders from the same allogeneic donor at a 1:2 ratio in MLC. T-cell alloreactivity was measured by 3H-Thymidine incorporation assay after 6 days of culture. Results are the mean SI ± SD of 4 separate experiments. ^*P = .05.