Stem Cells, HLA Antigens and Cell Therapy

Cell therapy is essentially a single-cell transplantation. Hence their main constraint is the same as in organ transplantation: the HLA histocompatibility. HLA antigens are proteins that cells express and present in their cell membranes. They are all specialized somatic cells, daughter cells of stem cells.       Each person has their characteristic HLA antigens. For the cells represent the same as the number of national identity for people. It is very difficult to find two people with the same identification code. Only identical twins and clones are assured of having identical HLA.       HLA antigens are used to recognize self from foreign. The cells recognize each other as sisters, showing their HLA antigens in their cell membrane. If they are identical, shake, if recognized as foreign, destroys the immune system rejection response.       HLA antigens are proteins that are exposed on the outer cell membrane of all somatic cells but not in stem cells. Some viruses can bind to HLA and use them as gateways to the cell interior. Fortunately, stem cells are not HLA antigens, so that go unnoticed to the virus and to the Immune Response System for rejection of any organism.       If transplanted adult stem cells and / or embryo of a person to another with different HLA, the receiver does not recognize them as foreign because they have no HLA antigens. But when production of daughter cells or somatic begins to present HLA antigens in their membranes, are recognized as foreign and destroyed by the receiver. This rejection can last war until the last foreign stem cell exhausts its last cell division and dies.