Summary Interleukin‐23 (IL‐23) is a member of the IL‐12 family of cytokines with pro‐inflammatory properties. Its ability to potently enhance the expansion of T helper type 17 (Th17) cells indicates the responsibility for many of the inflammatory autoimmune responses. Emerging data demonstrate that IL‐23 is a key participant in central regulation of the cellular mechanisms involved in inflammation. Both IL‐23 and IL‐17 form a new axis through Th17 cells, which has evolved in response to human diseases associated with immunoactivation and immunopathogeny, including bacterial or viral infections and chronic inflammation. Targeting of IL‐23 or the IL‐23 receptor or IL‐23 axis is a potential therapeutic approach for autoimmune diseases including psoriasis, inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. The current review focuses on the immunobiology of IL‐23 and summarizes the most recent findings on the role of IL‐23 in the pre‐clinical and ongoing clinical studies.

The existence and multiplicity of periodic solutions are obtained for the nonau-Ž . tonomous second order systems with locally coercive potential; that is, F t, x ª < < w x qϱ as x ª ϱ for a.e. t in some positive-measure subset of 0, T , by using an analogy of Egorov's Theorem, the properties of subadditive functions, the least action principle, and a three-critical-point theorem proposed by Brezis and Nirenberg. ᮊ

Some existence theorems are obtained by the least action principle for periodic solutions of nonautonomous second-order systems with a potential which is the sum of a subconvex function and a subquadratic function.

No abstract

Abstract. The existence and multiplicity of periodic solutions are obtained for nonautonomous second order systems with sublinear nonlinearity by using the least action principle and the minimax methods.