The key difference between endogenous and exogenous antigens is that the endogenous antigen is generated within the cells while the exogenous antigen enters the body from the outside.
Antigen is a molecule or a substance that reacts to a product of a specific immune response and stimulates antibody generation. Antigenicity of that particular molecule is the ability of an antigen to induce antibody production. Also, antigens can be either a protein or a polysaccharide. Furthermore, antigen-presenting cells (APCs), such as dendritic cells mediate the processes of antigen uptake, antigen processing, and antigen presentation. Moreover, depending on the immune activity, antigens can be classified as immunogens, tolerogens, or allergens. Besides, we can also classify antigens according to their origin as exogenous or endogenous.
