Interleukin 7 induces tcr gene rearrangement in adult marrow-resident murine precursor T cells

Rearrangement of the T cell antigen receptor genes is a complex, highly regulated process. To gain a better understanding of the extracellular factors involved in the regulation of TCR β and γ and gene rearrangement in adult murine bone marrow-resident precursor T cells, several cytokines were tested for their ability to induce gene recombination. A selected population of C58/J bone marrow cells (Thy l low, CD3 −, CD8 −, B220 −) that is enriched for pre-T cell activity was propagated in vitro in medium supplemented with IL-3 and mast cell growth factor (MGF, also referred to as stem cell factor, Steele factor and c-kit ligand). These cytokines were required for the maintenance of pre-T cell activity in culture, but had no effect on TCR gene expression. Several additional cytokines were added to the culture medium. Of all those tested, only IL-7 induced complete rearrangement of the TCR 7 locus. Complete rearrangement of the TCR β locus was not induced under any of the culture conditions analysed here. The bone marrow cells cultured in IL-3, MGF and IL-7 did not begin to express mature T cell proteins and maintained their in vivo progenitor potential. Furthermore. IL-7 cultured bone marrow cells were capable of differentiation in vivo into all phenotypic subpopulations of T cells, without an apparent bias toward the γλ lineage. The data presented here suggest that TCR γ gene rearrangement in adult pre-T cells is regulated by IL-7, but that the TCR β locus requires additional or alternative signals for the induction of complete rearrangement