Though a range of hematopoietic cells, including monocyte-macrophages, B lymphocytes, eosinophils, and dendritic cells, as well as columnar epithelial cells, have been found to be infected by HIV-1, the CD4-positive helper T lymphocyte has been identified as the primary target for HIV-1 infection [15]. Here, CD4 is linked to HIV-1 infection.