Figure 10. Summary and hypothesis.
(A) Mouse astrocytes and (B) human astrocytes appear to have distinct intracellular signaling mechanims in response to IL-1 or TLR ligands. LPS activated mouse astrocytes only. While human astrocytes responded robustly to IL-1, mouse astrocytes lacked similar responses to IL-1. In addition, mouse and human astrocytes also showed significant differences in their responses to poly IC. Poly IC induced high levels of TNFα and iNOS (“A1” genes) in mouse astrocytes, but not in human astrocytes. Remarkably, LPS induced little or no immunoregulatory genes (IFNβ, IP-10, RANTES and IL-27: “A2” genes) in mouse astrocytes, many of which are IRF3-dependent. Instead, these genes were robustly induced by poly IC, as in human astrocytes. See Figure 2 and also text for details.