The present invention relates to a method of inhibiting the upregulation of the expression of the proinflammatory cytokine interleukin-22 (IL-22) in activated and differentiated human T-cells, said upregulation being induced by administration of a therapeutically effective amount of a phosphodiesterase 4 (PDE4) inhibitor. The method comprises administering, either sequentially to or simultaneously with the administration of the PDE4 inhibitor, a vitamin D receptor agonist in an amount sufficient to inhibit the upregulation of IL-22 expression.
