CHARACTERIZATION OF HUMAN CD7 TRANSGENIC MICE

CD7 is a 40-kDa transmembrane glycoprotein member of the Ig gene super family expressed on most peripheral blood T lymphocytes and NK cells. CD7 is also expressed on myeloid, NK, B, and T cell precursors during adult hematopoiesis. Because Thy-1 is absent in human thymocytes and p eripheral blood T cells and shows structural similarities to the human CD7 gene, we have suggested that human CD7 may be a functional homolo gue in humans of mouse Thy-1. To study the tissue-specific expression of the CD7 gene utilizing its own promoter, we constructed transgenic mice that contained both the coding and flanking regions of the human CD7 gene. We found that human CD7 was expressed in transgenic mice in T, B, NK, and myeloid lineages and was induced with T cell activation. Unlike the expression of CD7 in humans, the CD7 transgene was present on mature B lymphocytes and macrophages. Like mouse Thy-1, transgenic human CD7 was expressed in immature and mature T cells and in Sca-1() bone marrow mononuclear cells. Unlike mouse Thy-1, the human CD7 tra nsgene was not expressed in mouse brain or fibroblasts. The human CD7 transgene was expressed during fetal development before mouse Thy-1 in fetal liver mononuclear cells. Expression of the human CD7 transgene did not alter mouse thymopoiesis or Thy-1 expression. Taken together, these data demonstrated that the CD7 transgene contained sufficient re gulatory regions to direct hematopoietic expression and mitogenic indu ction. The pattern of CD7 transgene expression more closely resembled that of CD7 in humans than that of mouse Thy-1.