Immune Cell (image) Washington University School of Medicine Caption This image shows an immune cell moving toward a light beam (blue box). The opsin in the cell (red) senses light and triggers the formation of new structures of the cell skeleton (yellow) that allow the cell to move. Credit Copyright PNAS, used with permission Usage Restrictions None 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.