Michael D.L. Johnson portrait (IMAGE) University of Arizona Health Sciences Caption Michael Johnson, PhD, is an associate professor of immunobiology at the College of Medicine – Tucson. Credit U of A Office of Research, Innovation and Impact Usage Restrictions U of A Office of Research, Innovation and Impact License Original 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.