Soluble HLA: patterns of expression in normal subjects, autoimmune diseases, and transplant recipients

Human leukocyte antigens ( HLA) are prominently expressed on the surface of lymphoid and other nucleated cells. These cell- surface molecules are anchored in the cell membrane and also have a short polypeptide domain. HLAs are highly polymorphic and, based on molecular structure, are grouped in two classes of antigens; class I and class II. Both of these antigens are encoded by a tightly linked series of genes on chromosome 6, called the major histocompatibility complex ( MHC).