Most people think of immune responses to a pathogen in terms of antibodies fighting the virus, bacteria or fungus. However, there’s another way in which the immune system fights infections, using a cell-mediated immune response. This response refers to several different types of cells that attack the infection without using antibodies.
Deeper Dive
The best-known of these other cell types are T cells. Killer T cells (CD8 cells), like antibodies, recognize the antigen on pathogens to identify an infected cell and then, as their name suggests, directly kill the infected cells by releasing toxins.
Helper T cells (CD4 cells) “recruit” other cells, including killer T cells and antibody-producing B cells, and coordinate attacks on infected cells, including releasing cytokines that participate in the attack. (This video is a good explainer.) Other cells involved in cell-mediated immunity include macrophages and natural killer (NK) cells, both types of white blood cells. Macrophages surround and destroy the pathogen itself, and natural killer cells destroy infected and diseased cells.