A prominent feature within the histopathological changes of psoriatic lesions is the particular spatial distribution of neutrophils, macrophages, and T-cell which are considered to participate in the pathogenesis of psoriasis. In this study, an attempt has been made to examine the microanatomical localization and magnitude of expression of the T-cell-attractant and -stimulating C-X-C and C-C chemokines Mig, interferon-inducible protein-10 (IP-10), macrophage inflammatory protein-1 alpha and 1 beta (MIP-a alpha and 1 beta), and regulated on activation, normal T-cell expressed and secreted (RANTES). Employing in situ hybridization, Mig message was strongly and selectively expressed in the upper lesional dermis with pronounced clustering in the tips of the papillae, whereas expression in normal or uninvolved skin was quiescent. In contrast, message for all the other chemokines investigated was much weaker or lacking. Expression of Mig transcripts in cell clusters of the papillae was paralleled by Mig immunoreactivity on endothelial and mononuclear cells. The expression profile, with high levels of Migs virtually limited to those lesional papillae with a pronounced infiltration of mononuclear leukocytes, strongly suggests that Mig is produced by a local population of highly activated macrophages and dermal microvascular endothelial cells. Considering the T-cell-attracting and -stimulating capacity of Mig and the importance of T-cells in the pathogenesis of psoriasis, this study indicates that this novel C-X-C chemokine plays an important role as a mediator of T-cell recruitment and activation in the papillae and thus contributes significantly to the cytokine network of inflammation in psoriasis.