Astrocytes are the major intracerebral source of macrophage inflammatory protein-3α/CCL20 in relapsing experimental autoimmune encephalomyelitis and in vitro

Macrophage inflammatory protein-3alpha/CCL20 is a recently identified chemokine that binds to CCR6 and acts as a chemoattractant for memory/differentiated T-cells, B-cells, and immature dendritic cells. We have previously reported that CCL20 and CCR6 mRNAs are expressed in the CNS of SJL mice with experimental autoimmune encephalomyelitis (EAE) and that CCL20 is produced by CNS-infiltrating leukocytes at disease onset and, additionally, by intraparenchymal astrocyte-like cells during disease relapses. In this study, we provide further immunohistochemical evidence that astrocytes represent the main CNS source of CCL20 during EAE. Moreover, we show that the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-a, but not interferon-gamma, induce expression of CCL20 mRNA and secretion of CCL20 protein in cultures of mouse brain-derived astrocytes. We also show that supernatants from cytokine-activated astrocytes stimulate the migration of polarized T helper cells and that this effect is partially inhibited by anti-CCL20 antibody. These findings suggest that, through secretion of CCL20, astrocytes could play an important role in orchestrating the recruitment of specific leukocyte subsets to the inflamed CNS and in regulating CNS-targeted immune responses.