Nomenclature for factors of the HLA system, update March 2012*

Immunology of hematopoietic stem cell transplant

Hematopoietic stem cell transplantation (HSCT) is a procedure in which infusion of hematopoietic stem cells is used to reestablish hematopoietic function in patients with damaged or defective bone marrow or immune systems. Early and late complications following allogeneic HSCT include acute and chronic graft-versus-host disease (GVHD), donor rejection, graft failure, relapse of primary malignancy, conditioning-related toxicity, immunodeficiency and infections. Immunology has a central role in allogeneic hematopoietic cell transplantation. Any appreciation of the immunological mechanism involved in engraftment, GVHD, the development of tolerance, immune reconstitution, and the control of malignancy requires some understanding of the immunologic basis for immune reactions provoked by grafting tissue from one individual to another. In the future it should be possible to learn what gene(s) must be activated and which must be repressed to force stem cells into division without maturation; to engineer a mechanism into the cells that stops proliferation and sets the stage for amplification; to search if there could be a universal donor cell line, neatly packaged and stabilized in sealed vials and distributed by the pharmaceutical industry; to modify the transplanted cells in such a way that they have a proliferative advantage over those of the host and to deliver the lethal blow against the neoplasm, perhaps the cells that are infused will be engineered in such a way as to be able to distinguish between normal host cells and tumor.

The Role of HLA in Cord Blood Transplantation

In recent years, umbilical cord blood (CB), a rich source of hematopoietic stem cells (HSC), has been used successfully as an alternative HSC source to treat a variety of hematologic, immunologic, genetic, and oncologic disorders. CB has several advantages, including prompt availability of the transplant, decrease of graft versus host disease (GVHD) and better long-term immune recovery, resulting in a similar long-term survival. Studies have shown that some degree of HLA mismatches is acceptable. This review is intended to outline the main aspects of HLA matching in different settings (related, pediatric, adult, or double-unit HSCT), its effect on transplantation outcome and the role of HLA in donor selection.