VIP generates human tolerogenic DCs, which induce IL-10-producing anergic CD4 T cells. Human DCs generated in the absence (DC_controls, ▪) or presence (DC_VIPs, □) of VIP were stimulated with LPS to induce DC activation/maturation. (A) Purified naive CD4 T cells were cultured with graded doses of allogeneic DC_controls (▪) or DC_VIPs (□) in primary cultures (panel i). CD4 T cells from primary cultures were recovered, rested, and restimulated with LPS-matured allogeneic DCs (panel ii). Cultures of DC_controls or DC_VIPs without T cells did not proliferate. Cytokine production was determined in secondary cultures at DC/T cell ratios of 1:10 (panel iii). Each result is the mean ± SD of 3 experiments performed in duplicate. (B) TT-primed T_H1 cells were cocultured with TT-pulsed syngeneic DC_controls (▪) or DC_VIPs (□)in primary cultures (panel i). After 3 days of culture, T_H1 cells were rescued, rested, and restimulated with TT-pulsed, LPS-matured syngeneic DCs, and proliferation (panel ii) and IFNγ production (panel iii) were determined. Unpulsed or ovalbumin-pulsed DC_controls or DC_VIPs did not induce the proliferation of TT-primed T_H1 cells. Each result is the mean ± SD of 3 experiments performed in duplicate.