TNF and vasculitis: In order to maximise the number of human neutrophils in the circulation at the time of antibody injection, and guided by prior investigations in vitro that indicated ANCA activity is markedly enhanced following neutrophil or endothelial exposure to TNFα or LPS, we determined to administer low-dose LPS to all groups of chimera mice prior to injection of human IgG in order to mobilize neutrophils into the circulation and increase the likelihood of triggering vasculitis [10].