Human T lymphocyte priming in vitro by haptenated autologous dendritic cells

Dendritic cells (DC), generated from adherent peripheral blood mononuclear cells (PBMC) by culturing with granulocyte-macrophage colony-stimulating fa ctor (GM-CSF) and IL-4, were used to study in vitro sensitization of naive, hapten-specific T cells and to analyse cross-reactivities to related compo unds. DC were hapten-derivatized with nickel sulphate (Ni) or 2-hydroxyethy l-methacrylate (HEMA), followed by tumour necrosis factor-alpha (TNF-alpha) -induced maturation, before autologous T cells and a cytokine cocktail of I L-1 beta, IL-2 and IL-7 were added. After T cell priming for 7 days, wells were split and challenged for another 7 days with Ni or HEMA, and potential ly cross-reactive haptens. Hapten-specificity of in vitro priming was demon strated by proliferative responses to the haptens used for priming but not to the unrelated haptens. Highest priming efficiencies were obtained when b oth IL-4 and IL-12 were added to the cytokine supplement. Marked interferon -gamma (IFN-gamma) release (up to 4 ng/ml) was found when IL-12 was include d in the cultures, whereas IL-5 release (up to 500 pg/ml) was observed afte r addition of IL-4 alone, or in combination with IL-12. Nickel-primed T cel ls showed frequent crossreactivities with other metals closely positioned i n the periodic table, i.e. palladium and copper, whereas HEMA-primed T cell s showed distinct cross-reactivities with selected methacrylate congeners. Similar cross-reactivities are known to occur in allergic patients. Thus, i n vitro T cell priming provides a promising tool for studying factors regul ating cytokine synthesis, and cross-reactivity patterns of hapten-specific T cells.