Cell-mediated immunity develops through a network of interactions that results in defense against microorganisms that survive within phagocytes or other cells. The response is initiated by the recognition of intracellular microorganism antigen by T cells through the histocompatibility complex. In the CD8 response, only the target cell carrying the class I associated antigen can be lysed or induced to apoptosis. In another mechanism of the cellular response, CD4 + Th1 T cells activate, for example, cytokine-infected macrophages such as IFN. When a pathogen resists the effects of activated macrophages, chronic infection may develop.
The hormonal immunity response leads to the destruction of extracellular microorganisms and prevents or decreases the spread of intracellular cells by neutralizing, opsonizing and activating the complement system.
