Major and Minor Histocompatibility Antigens to Non-Inherited Maternal Antigens (NIMA)

Immunological reactivity results from differences between the transplant host and donor for cell surface determinants known as histocompatibility antigens. Histocompatibility antigens that provoke the most severe transplant reactions are encoded by a series of genes that reside in a discrete chromosomal region termed the major histocompatibility complex (MHC) (Amos 1968). Genes of the human leukocyte antigen (HLA) system encode a complex array of histocompatibility molecules that play a central role in immune responsiveness and in determining the outcome of hematopoietic stem cell transplantation (HSCT) (Beatty, Anasetti et al. 1993; Petersdorf, Longton et al. 1995). The primary goal of histocompatibility testing for patients who are undergoing HSCT is the identification of a suitable HLA-matched donor to reduce the risk of post-transplant complications, which may result from HLA incompatibility. The extensive polymorphism of the HLA system, however, makes the selection of a comprehensively, optimallymatched donor a challenging endeavor, particularly when donors outside of the patient’s immediate family are sought. If a suitable donor is not found, clinicians need to explore the possibility of permissive HLA mismatches.