SOCS proteins in T helper cell differentiation: implications for allergic disorders?

Asthma, allergic rhinitis and atopic dermatitis are allergic immune disorders characterised by a predominance of T helper 2 (Th2) cells, the resulting elevation of allergen-specific IgE, and mast-cell- and basophil-associated inflammation. The cytokine environment at the site of the initial antigen stimulation determines the direction of Th-cell differentiation into Th1 or Th2 cells. The SOCS (suppressor of cytokine signalling) proteins are implicated in the control of the balance between Th1 and Th2 cells in this process. SOCS3 is predominantly expressed in Th2 cells and inhibits Th1 differentiation; conversely, SOCS5 is expressed predominantly in Th1 cells and inhibits Th2 differentiation. Here, we discuss the role of SOCS proteins in Th-cell differentiation and explore the potential of SOCS proteins as targets for therapeutic strategies in allergic disorders.