Cytokines in giant-cell arteritis.

Cytokines are small proteins that serve as chemical messengers between cells, regulating cell growth and differentiation, tissue repair and remodeling, and many aspects of the immune response. Cytokines are instrumental in determining the nature, magnitude, and duration of inflammatory reactions and, as such, represent ideal targets for interfering with pathogenic processes. In OCA and PMR, cytokines are encountered in two locations, the inflammatory infiltrates accumulating in the arterial wall and in the circulation. IL-6, a cytokine involved in stimulating acute-phase responses, is located upstream of many of the laboratory abnormalities considered helpful in diagnosing and managing GCA/PMR, including elevated ESR and CRP. IL-6 has the potential to be helpful in predicting disease severity and may allow for a tailoring of immunosuppressive therapy. There is evidence suggesting that IL-6 outperforms other chemical markers in detecting disease activity and could, therefore, have a role in monitoring treatment. Interesting pathogenic clues have been derived from studies of cytokines produced in the vascular lesions. IFN-gamma has emerged as a key regulator in determining the nature and direction of the inflammatory response. IFN-gamma appears to be critically involved in modulating the process of intimal hyperplasia, the most destructive consequence of vasculitis, and, as such, emerges as a prime target for novel therapeutic approaches.