Mouse CD4 enhancer sequences, the human CD4 promoter, 8.8 kb of HIV sequences, and an SV40 polyadenylation signal was used for the transgene. The enhancer and promoter sequences were used to drive expression in CD4+ T cells and cells of the dendritic/macrophage lineage. Northern blot analysis showed high transgene expression in the thymus, moderate expression in spleen and lymph nodes, and weak expression in kidneys, lungs, intestines, and liver.