Autoimmunity - an Introduction
Acquired Immunity - B Cells
B cells are important for the humoral immune response: They produce antibodies (immunoglobulins) against foreign invaders in the body fluids (humour). After an infection they develop into memory B cells, thereby contributing to immune memory. They are immediately able to initiate a strong immune response after a second contact with the same pathogen.
During lifetime, the body produces millions of different B-cells. Every B cell generates a single characteristic type of antibody and displays it on the surface like a flag. Via this membrane bound antibody the B cell recognizes and binds to only one specific antigen.
T cell-/ B cell-cooperation
The principal functions of B cells are to produce antibodies against (auto-) antigens and to perform the role of antigen-presenting cells (APCs). If a B cell encounters the matching antigen, e.g. a virus, this antigen binds to the membrane bound antibody on the B cell surface. The B cell internalizes and degrades the virus, and transports the resulting peptides bound to a MHC class II molecule to the cell membrane and displays it on the cell surface.
The appropriate activated T helper cell may now bind to the antigen on this B cell. Direct interaction via cell-cell contact of a B cell and an activated T helper cell stimulates the T cell to produce interleukins that initiate B cell division and maturation.
Adaptive and innate components of the immune system are closely meshed together via a network of chemical modulators and direct cell-cell contacts. By coordinating the interaction of all innate and adaptive immune mechanisms the body is able to exert an efficient immune response.