Mitogen

A mitogen is a chemical, usually some form of a protein, that encourages a cell to commence cell division, triggering mitosis.

Mitogens trigger signal transduction pathways in which mitogen-activated protein kinase is involved, leading to mitosis.

Use in immunology
Plasma B cells can enter mitosis when they encounter an antigen matching their immunoglobulin.

Mitogens are often used to stimulate lymphocytes and therefore assess immune function.

The most commonly used mitogens in clinical laboratory medicine are:

Lipopolysaccharide toxin from gram negative bacteria is thymus independent. They may directly activate B cells, regardless of their antigenic specificity.

Plasma B cells are terminally differentiated and therefore cannot undergo mitosis. Memory B cells can proliferate to produce more memory cells or plasma B cells. This is how the mitogen works, by inducing mitosis in B cells to cause them to divide, with some becoming plasma cells.

Other uses
Mitogens also induce the activity of the COX-2 enzyme.