Covid-19 Update Recent research throws light on the significance of the role T-cells play in immune response against the coronavirus Print edition : April 23, 2021 T+ T- A scanning electron micrograph of a human T lymphocyte (also called as a T-cell) from the immune system of a healthy donor. Cellular immunity is mediated by T-cells, which tailor the immune response to a specific pathogen, say a virus. Photo: National Institute of Allergy and Infectious Diseases, U.S. A scanning electron micrograph showing a dying cell infected with the coronavirus (viral particles in red). Photo: National Institute of Allergy and Infectious Diseases/The New York Times