TNF and infection: As a means of bypassing the endothelial activation and potentiation requirement for B. burgdorferi to transmigrate the endothelium, these processes can be promoted by injection of mice with one of several cytokines (IL-10, MCP-1, or TNF-α), which can rapidly prepare the endothelium for spirochete extravasation within 3 h of infection, rather than the 24-h time period required during a normal infection (16).