T-cell development in the absence of the pre-T-cell receptor

The development of pre-T-cells with productive T-cell receptor beta (TCR beta) rearrangements can be furthered by each of the pre-T-cell receptors (pre-TCR), the alpha beta TCR as well as the gamma delta TCR, albeit by distinct mechanisms. While the gamma delta TCR affects CD4-8- precursor cells irrespective of their TCR beta rearrangement status both the pre-TCR and the alpha beta TCR select only cells with productive TCR beta genes for expansion and maturation. The alpha beta TCR is much less effective than the pre-TCR because of the paucity of TCR alpha proteins in TCR beta positive precursors.