What is the Difference Between Endogenous and Exogenous Antigens?

The main difference between endogenous and exogenous antigens lies in their origin and location within the body.

• Endogenous antigens are found within the cytosol of human cells, such as viral proteins, proteins from intracellular bacteria, and tumor antigens. These antigens are generated due to cell metabolism or viral or intracellular bacterial infection.
• Exogenous antigens enter the body from the outside, such as bacteria, fungi, protozoa, and free viruses. These antigens can enter the body through inhalation, ingestion, or injection and are typically found in foreign substances.

Both endogenous and exogenous antigens can stimulate an immune response, but the manner in which they are presented to the immune system differs. Endogenous antigens need to be presented to the immune system via specialized cells called antigen-presenting cells (APCs), which include dendritic cells, macrophages, and B cells. In contrast, exogenous antigens can be recognized by the immune system directly upon entering the body.

Comparative Table: Endogenous vs Exogenous Antigens

The main difference between endogenous and exogenous antigens lies in their origin. Here is a table comparing the two types of antigens:

Endogenous antigens are generated within the cells due to cell metabolism, viral infections, or intracellular bacterial infections. On the other hand, exogenous antigens enter the body via inhalation, ingestion, or injection from outside sources, such as bacteria, viruses, fungi, protozoa, and helminths. Both types of antigens can induce an immune response, leading to the production of antibodies and activation of T cells.