Mitogen

Mitogens are stimulating cell division proteins.

Immunology

Mitogenic stimulate cell division in at B and T cells. Antigens during the B and T cells can be activated only by specifically binding receptors (genuine immune response), mitogens respond by stimulation of these cell types ( no specific immune response). Because of this ability, they are referred to as polyclonal activators.

A major mitogen group are lectins (sugar -binding proteins) that bind specifically to glycoproteins of various cells, including lymphocytes. Lectins often lead to agglutination what cell activation and proliferation entails. Some lectins specifically activate B- cells, other T- cells only, and others, both cell types.

Known Lectins are:

• Concanavalin A ( ConA) (T- cell activation )
• Phytohemagglutinin (PHA) (T- cell activation )
• Pokeweed mitogen (PWM = pokeweed ) (B- and T-cell activation).

Not all lectins are mitogens. Lipopolysaccharides (LPS) from the cell walls act of Gram-negative bacteria mitogenic for B cells. So-called superantigens are the most potent T-cell mitogens. They link the major histocompatibility complex ( MHC II) an antigen presenting cell (APC ) and the T-cell receptor of a helper or cytotoxic T- cell by outside attach to the two molecules. The binding is antigen - independent. The T- cells are activated and produce cytokines in excess.

Known superantigens include the enterotoxin A and the TSS toxin of Staphylococcus aureus, which can cause the sometimes fatal toxic shock syndrome (TSS ) and staphylococcal enterotoxin B ( SEB).