Protein S Made Visible (image) University of Arizona Caption In this microscopic image, three cells of the innate immune response (red with blue cell nuclei) are seen next to two T-cells. T-cells appear blue when they're not active. Only when they make contact with and are activated by the innate cells do the T-cells turn on Protein S, causing them to glow green. Credit Lidia Bosurgi Usage Restrictions This visual may only be used in conjunction with reporting/posting of this news release. Image/video credit must be included exactly as indicated. 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.