γc gene transfer in the presence of stem cell factor, FLT-3L, interleukin-7 (IL-7), IL-1α, and IL-15 cytokines restores T-cell differentiation from γc(-) X-linked severe combined immunodeficiency hematopoietic progenitor cells in murine fetal thymic organ cultures

X-linked severe combined immunodeficiency (SCID-XI) is a rare human inherited disorder in which early T and natural killer (NK) lymphocyte development is blocked. The genetic disorder results from mutations in the common gamma c chain that participates in several cytokine receptors including the interleukin-2 (IL-2), IL-4, IL-7, IL-9, and IL-15 receptors. We have shown in a previous report that gamma c gene transfer into SCID-XI bone marrow (BM) cells restores efficient NK cell differentiation. In this study, we have focused on the introduction of the gamma c gene into SCID-XI hematopoietic stem cells with the goal of obtaining differentiation into mature T cells. For this purpose, we used the in vitro hybrid fetal thymic organ culture (FTOC) system in which a combination of cytokines consisting of stem cell factor (SCF), Flt-3L, IL-7, IL-1 alpha, and IL-15 is added concomitantly. In this culture system, CD34(+) marrow cells from two SCID-XI patients were able to mature into double positive CD4(+) CD8(+) cells and to a lesser degree into CD4(+) TCR alpha beta(+) single positive cells after retroviral-mediated gamma c gene transfer. In addition, examination of the output cell population at the TCR DJ beta 1 locus exhibited multiple rearrangements. These results indicate that restoration of the gamma c/JAK/STAT signaling pathway during the early developmental stages of thymocytes can correct the T-cell differentiation block in SCID-XI hematopoietic progenitor cells and therefore establishes a basis for further clinical gamma c gene transfer studies. (C) 1998 by The American Society of Hematology.