Rearrangement of IgH genes in normal thymocyte development.

IgH chain gene segments are rearranged in 30 to 50% of peripheral T cells. We have analyzed IgH gene rearrangements during normal T cell development, using a well characterized collection of hybridomas derived from fetal, newborn, adult, or aged thymocytes. Our results show that IgH rearrangements occur in the thymus after T cell receptor gene and T cell specific gamma-gene rearrangements but before thymocyte maturation is completed. Therefore IgH gene rearrangements occur at an intermediate stage in thymocyte development. This may be of significance in delineating human lymphoid leukemias. Not all thymocyte hybridomas carried IgH gene rearrangements. Age-related shifts in frequencies of cells with IgH gene rearrangements, probably indicating changes in the composition of thymocyte populations, were found. Finally, a detailed analysis of D to J joins revealed an ordered progression of partial rearrangements at the IgH locus, whereby the most proximal DH-segment, DQ52, is used predominantly at early stages, but that other D to J rearrangements at the same locus may occur subsequently.