Distinct regulatory elements are required for faithful expression of human CD4 in T cells, macrophages, and dendritic cells of transgenic mice.

To identify the regulatory elements controlling expression of the human CD4 (hCD4) gene in different cell types of the immune system, deletion and chimeric (human/murine) reporter genes were constructed and tested in transgenic (Tg) mice. Regulatory elements required for the proper hCD4 expression in the immature double-positive thymic T cells were identified in the enhancer and in the 3' end of intron 1. Expression of hCD4 in macrophages is controlled by at least 2 sets of regulatory elements: one present in front of exon 1 and the second at the 5' end of intron 1. The hCD4 elements required for expression on both myeloid and lymphoid CD8alpha(+) dendritic cells (DCs) from lymph node and thymus were found to be different from those required for macrophage expression. The results indicate that expression of hCD4 in T cells, macrophages, and DCs is controlled by distinct regulatory elements.