Dr. Unanue then showed that the foreign antigens are peptides.

For example, the follicles expand significantly upon encountering a foreign antigen.

Cytokines signal to other immune cells that there is a foreign antigen present.

Therefore, T cells need a region where they can go to sample foreign antigens that have entered the body.

A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen.

This causes a B cell response, wherein antibodies are produced against the foreign antigen.

Their function is to sense foreign antigens, and hence the presence of 'foreign' proteins.

The mechanism by which foreign antigens are presented to T lymphocytes is central to the whole of immunology.

Children are exposed to many foreign antigens every day.

Alloimmunity is an immune response to foreign antigens (alloantigens) from members of the same species.