γδ T cells activate DCs in vitro and in vivo. Intestinal intraepithelial lymphocytes were sorted into γδ⁺ and γδ^- populations. BM-derived DCs were then cultured with either γδ⁺ T cells (γδ+), γδ^- T cells (γδ^-), LPS, or medium. Allogeneic not T-cell proliferation was determined. DCs were isolated on a metrizamide gradient and the expression of CD40 was evaluated by FACS (B). The solid line denotes CD40 expression. The dashed line denotes the IgG negative control. These DCs were irradiated and then cultured with allogeneic BALB/c responder T cells that were assayed for proliferation (A). DCs plus γδ⁺ vs DCs plus γδ^-, ^*P < .05. Responder BALB/c T cells were cultured for 3 to 4 days with irradiated B6 DCs that had been previously cultured for 36 hours with (C) wt γδ T cells with and without anti-IFN-γ mAb or with γδ T cells from IFN-γ-deficient (IFN-γ^-/-) mice; (D) irradiated CD40-deficient (CD40^-/-) DCs; (E) wt γδ T cells with and without anti-CD40L mAb (DCs plus γδ T) or separated by a 0.2 μ transwell membrane (DCs/γδ T transwell). During the final 12 hours of culture, cells were pulsed with [³H] thymidine and assayed for proliferation. DCs plus γδ T vs DCs/γδ T transwell, ^**P < .05. Each graph represents 1 of 3 to 4 similar experiments. Data represent the mean ± SE.