Regulation of T Cell Activation by CD28 and CTLA4
T cell activation is initiated by engagement of the T cell receptor (TCR)-CD3 complex by antigen displayed by major histocompatibility complex (MHC) molecules expressed on the surface of an antigen presenting cell (APC). However, under most circumstances, this initial signal is insufficient to induce a proliferative response. TCR engagement in the absence of a second or costimulatory signal can lead to a state of anergy or cell death1. CD28 is a T cell surface receptor capable of providing this critical second signal following ligation of the B7 family of counter-receptors that are expressed on APCs2,3. This interaction provides not only proliferative signals, but also crucial survival signals that are important for both initiation and maintenance of an immune response4,5.
KeywordsMajor Histocompatibility Complex Programme Cell Death Cell Death Pathway Immune Homeostasis Wildtype Mouse
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