Regulatory T cell - Definition

Regulatory T cells (also known as suppressor T cells) are characterised by virtue of their expression of the cell surface markers CD4 and CD25. They help to suppress or prevent autoimmunity by counteracting self-reactive lymphocytes. Some (but not all) do so by secreting inhibitory cytokines that block the activation of macrophages or other lymphocytes. It is unclear what factors cause immature T cells to develop into regulatory T cells, but they may do so in thymus or in peripheral tissues