IL-12 is a cytokine produced by dendritic cells (DC) and activates cytotoxic T cells and NK cells against tumors. We investigated the effect of IL-12 on DC. When peripheral blood monocytes were incubated with canine granulocyte-macrophage (GM)-CSF and IL-4, expression of MHC class II, CD1a, CD80 and CD86 was significantly elevated, but the cell morphology was that of immature DC. By adding canine IL-12 to the DC-inducing culture, expression of CD80 and CD1a was significantly enhanced, and the cell morphology shifted to that of mature DC. T cell stimulation by cultured cells was also significantly enhanced by the presence of IL-12. These results show that IL-12 significantly promotes the maturation and activation of canine DC following the induction of differentiation by GM-CSF and IL-4.
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