Purposeful Proliferation (IMAGE) Brown University Caption Working with colleagues including Professor Christine Biron, graduate student Margarite Tarrio helped discover that when 'natural killer' cells proliferate after infection, their role changes from from marshaling the immune response to regulating it. Credit David Orenstein/Brown University Usage Restrictions with 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.