Glia-T cell dialogue.

Interactions of CD4(+) T helper (Th) cells with microglia and astrocytes are likely to play an important role in regulating immune responses as well as tissue damage and repair during infectious and autoimmune central nervous system (CNS) diseases. T cells secreting Th1-type cytokines provide inducing signals for microglia to mature into functional antigen presenting cells (APC). The ability of microglia to act as efficient APC for the restimulation of Th1 cells suggests a role for these cells in the local amplification of pro-inflammatory immune responses. Conversely, the Th2-inducing capacity of microglia and astrocytes together with their ability to produce anti-inflammatory mediators could play a role in providing counter-regulatory signals limiting CNS inflammation. In this article, we review recent studies addressing the functional significance of T cell-CNS glia interactions and present new data on the expression of cyclooxygenase-2, the inducible enzyme involved in prostanoid biosynthesis, in microglia and astrocytes during the course of experimental allergic encephalomyelitis.