Cellular immunity is a type of immune response that primarily involves T cells, a kind of white blood cell. These cells recognize and destroy infected or cancerous cells in the body. Unlike humoral immunity, which uses antibodies to target pathogens, cellular immunity directly attacks infected cells, helping to control infections and prevent the spread of disease. The process begins when antigen-presenting cells display pieces of pathogens on their surfaces. T cells then bind to these antigens, activating them to proliferate and carry out their functions. This response is crucial for fighting off viruses and intracellular bacteria, as well as for tumor surveillance.