C5AR1 and systemic lupus erythematosus: As reported, C5a–C5aR promoted apoptosis in brain vascular endothelial cells of experimental lupus, lung cells of acute lung injury or murine kidney endothelial cells,87, 88, 89 but delayed apoptosis of human neutrophils via an extracellular signal‐regulated kinase and bad‐mediated signalling pathway.90