Recognising Self and Non-Self Cells

Lymphocytes are able to distinguish which cells are the body's own cells (self) and which cells are foreign (non-self) in order to destroy pathogens without destroying the body's own cells.Antigens are proteins and glycoproteins on the cell surface. Each type of cell has its own assortment of antigens on the cell surface. The primary structure of these proteins and glycoproteins gives the antigen its unique tertiary structure.There are about 10 million different types of lymphocytes each able to bind to one particular antigen. None of the lymphocytes are able to recognise or bind to the surface proteins on normal body cells but they may be able to recognise cancerous cells by their surface antigens. When an infection occurs lymphocytes that have the complementary receptors to the invading cell's antigens are stimulated to destroy the pathogen.Recognising Self Cells. In the fetus, lymphocytes are constantly colliding with fetal cells. Since the fetus is protected from infection by the mother's immune system, these lymphocytes collide with self cells only. Any lymphocytes that can bind to the antigens on fetal cells either undergo apoptosis (programmed cell death) or are suppressed.