Interleukin 21: A key player in lymphocyte maturation

Abstract

The common γ chain family of cytokine receptors plays a plethora of roles during the early development, activation, and terminal differentiation of the lymphocyte lineages. The most recently identified member of this family, the IL-21R, is expressed to varying degrees on B, T lymphocytes, and natural killer (NK) cells, whereas IL-21, is reportedly only produced by activated CD4 + T cells. In keeping with this expression pattern the IL-21:IL-21R interaction is important for the latter stages and function of all three lymphoid lineages. IL-21 is a regulator of B-cell differentiation to plasma cells as well as immunoglobulin class switching. In contrast, within the T-cell lineage, IL-21 acts as..