These changes may include upregulation of complement component 3 (C3).6,7 Divergent astrocyte reactive states have been shown when comparing inflammation with stroke.8 Recent work suggests that astrocytes can undergo protective or deleterious reactive changes, characterized by distinct gene expression signatures.6,9 Potential triggers for the reactive transformation of astrocytes include the release of cytokines (TNF-α, IL-1α) and complement (C1q) by neighbouring cells. The gene discussed is C3; the disease is Stroke.