Exogenous antigen

Exogenous antigens are molecules, particles, or substances that originate outside the host organism and are recognized as foreign by the immune system[4][5][9]. Examples include microbial proteins, polysaccharides, toxins, venom, allergens, and transplanted tissue proteins[3][4][9][10]. They typically enter the body via inhalation, ingestion, injection, or skin injury, and once inside, they are processed and presented by antigen-presenting cells (APCs) such as macrophages, dendritic cells, or B cells[3][5]. These antigens prompt the adaptive immune system—especially B cells and T cells—to mount a specific response, which can include the production of antibodies or activation of cytotoxic cells[2][3][4][5]. Antigens of this class are essential for the body's defense against infectious agents, but can also trigger undesirable reactions such as allergies or transplant rejection[4][5].

Other names

foreign antigenexternal antigennon-self antigen