ChT1, an Ig superfamily molecule required for T cell differentiation

The thymus is colonized by circulating progenitor cells that differentiate into mature T cells under the influence of the thymic microenvironment. We report here the cloning and function of the avian thymocyte Ag ChT1, a memb er of the Ig superfamily with one V-like and one C2-like domain. ChT1-posit ive embryonic bone marrow cells coexpressing c-kit give rise to mature T ce lls upon intrathymic cell transfer, ChT1-specific Ab inhibits T cell differ entiation in embryonic thymic organ cultures and in thymocyte precursor coc ultures on stromal cells. Thus, we provide clear evidence that ChT1 is a no vel Ag on early T cell progenitors that plays an important role in the earl y stages of T cell development.