Events That Regulate Differentiation of Alpha Beta TCR+ and Gamma Delta TCR+ T Cells from a Common Precursor

T cells in vertebrates are composed of two distinct lineages of cells distinguished by the type of antigen receptors they express: the conventional population expresses TCR composed of alpha beta heterodimers while a smaller fraction of mature T cells displays gamma delta TCRs on the cell surface. The alpha beta and gamma delta T cells develop from common T-cell progenitors and the alpha beta/gamma delta lineage commitment process should be viewed in the context of the diverse cell fate decision processes crucial for normal cell differentiation from a single pluiripotent stem cell. A major focus in this field has been to determine the role of TCR gene rearrangement and expression in alpha beta/gamma delta lineage commitment. In this review we summarize the current state of understanding in the pattern of TCR gene rearrangement and expression of alpha beta and gamma delta T cells to address this central question of whether or not the lineage commitment is dictated by the state of TCR gene rearrangement.