In response to pathogens, glial cells dynamically and differentially regulate Toll-like receptor gene expression

The mechanisms that mediate innate immune recognition of CNS infections are unknown. This study provides a comparison of Toll-like receptor (TLR) gene expression in resting and virus infected CNS cells. N2a neuroblastoma cells expressed TLR 3 but demonstrated no change in TLR gene expression in response to either LPS or virus infection. N9 microglia and differentiated primary astrocytes expressed most TLR genes. TLR 2 expression was highest in N9 microglia and TLR 7 in astrocytes. In both glial cell types, LPS stimulation upregulated pro-inflammatory cytokines, TLR 2 and TLR 3 gene expression but down-regulated other TLR genes. RNA virus infection substantially increased levels of type-I interferon (IFN) and TLR 3 transcripts and to a lesser extent TLR 9 transcripts. Microglia and astrocytes thus have the ability to discriminate between pathogens and elicit an appropriate response.