M2 Macrophages (IMAGE) Charité - Universitätsmedizin Berlin Caption Isolated M2 macrophages (blue nuclei and red dots) produce endogenous opioids such as enkephalin (green dots). Credit Machelska/ Charité Usage Restrictions This image may only be used with appropriate caption and credit. License Licensed content 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.