Macrophage-derived chemokine production by activated human T cells in vitro and in vivo: preferential association with the production of type 2 cytokines

Macrophage-derived chemokine (MDC), a potent chemoattractant for chronicall y activated Th2 lymphocytes, is constitutively expressed by dendritic cells , B cells, macrophages, and thymic medullary epithelial cells, whereas mono cytes, NK cells, and T lymphocytes produce MDC only upon appropriate stimul ation. In this study, we show in vitro MDC production also by activated T c ells, which preferentially associate with the production of Th2 cytokines, IL-4, IL-5, and IL-6, and inversely correlate with the production of the Th 1 cytokine, IFN-gamma. Moreover, high levels of MDC were detected in the se ra of the great majority of subjects suffering from mycosis fungoides/Sezar y syndrome or atopic dermatitis, which are considered as disorders characte rized by the predominant expansion and activation of Th2 cells, respectivel y. By contrast, serum MDC levels in subjects with multiple sclerosis or Cro hn's disease, which are characterized by a Th1 predominance, did not differ significantly from those of healthy controls. Finally, MDC expression was detected in the skin biopsy specimens of subjects with atopic dermatitis, w here it was expressed by both dendritic cells and T lymphocytes. Taken toge ther, these findings suggest that MDC production by activated T cells may o ccur both in vitro and in vivo, particularly in association with Th2 cytoki nes, thus providing an important amplification circuit for Th2-mediated res ponses.