TLR2 and infection: Under resting conditions, astrocytes express TLRs 2–4, and TLR2 and TLR4 may be upregulated on infection, as demonstrated with stimulation by lipopolysaccharide or treatment with poly(inosinic acid):poly(cytidylic acid) (polyI:C), which is a synthetic analog of dsRNA commonly used as a model of pathogen infections [79,80,81].