Basics of T Cell Development and Activation

T cells are defined by their development in the thymus from bone marrow-derived precursors and by heterodimeric receptors allied with the proteins of the CD3 complex. Mature T cells leave thymus and migrate into the peripheral lymphoid organs whereupon encounter with the fragment of foreign antigen proteins which are displayed by major histocompatibility complex (MHC) on the surface of antigen presenting cell (APC), they are activated and differentiate into effectors and memory T cells. The adaptive immune responses by T cells are important to protect the host against various types of pathogens. The present review will focus on the basic mechanism involved in the development and activation of T cells.