Weapon of the Immune System with a Built-In Safety Catch (image) University of Bonn Share Print E-Mail Caption In a urinary tract infection, the migration of neutrophils (red cell) from the blood (red vessel, above) to the infection is only possible following a consultation between helper (yellow) and sentinel macrophages (green). Via the positive signal of the helper macrophages (thumbs up), the sentinel macrophage produces the protein CXCL2 (key) which allows the neutrophils to migrate through the basal membrane of the uroepithelium (chain with lock). Credit Graphic: P. Schreiner and M. Gerhards/UKB Usage Restrictions The graphic may be used with the press release. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.