lymphocytes (or T cells) are the body’s single most important defence against viruses. There are two main types of T cells: helper T cells, characterized by the CD4 molecule on their surface, and killer (or cytotoxic) T cells, characterized by the CD8 molecule. Both CD4 and CD8 T cells kill virus-infected cells through the production of toxic chemicals that rupture the cell membrane, and CD4 T cells also produce cytokines that help CD8 T cells and B lymphocytes to grow, mature, and function properly.
