An isolated and purified cell line of hematopoeitic stem cells (HSC) that are incapable of expressing the CCR5 receptor on the cell surface (“the CCR5Δ32 cells” are used to regenerate the immune system in a subject in need thereof and especially to treat a subject infected with human immunodeficiency virus (HIV). The method is carried out by transplanting CCR5Δ32 into the recipient subject. Because mature immune cells derived from CCR5Δ32 cells cannot express functional CCR5 receptors, they will be resistant to infection by HIV and other pathogens that use the CCR5 receptor to infect cells. An embodiment of the invention includes administration of a nutritional regimen to the patient that optimizes conditions for CCR5Δ32 cell transplantation. Another embodiment of the invention includes co-transplanting mesenchymal cells along with the HSC in order to enhance the growth and development of the transplanted HSC.