A Secret to Making Macrophages (2 of 2) (image) California Institute of Technology Share Print E-Mail Caption Blood progenitor cells differentiate in a culture. The brightness of green indicates the amount of the regulatory protein PU.1 present. These images are from a time-lapse movie taken over the course of differentiation. Credit Hao Yuan Kueh, Michael Elowitz and Ellen Rothenberg/Caltech Usage Restrictions None 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.