An increasing number of gene polymorphisms of immune regulatory molecules are being associated with clinical performance following stem cell transplantation (SCT). These polymorphisms affect structural or regulatory changes on immune regulatory molecules including cytokines (1 –11 ), steroid hormone family receptors (12 ,13 ), pathogen effectors such as mannose binding lectins (14 ), and response mediators such as the Fas signaling system (15 ).
In contrast to polymorphisms of the major histocompatibility complex, the genome variations found in these non-human leukocyte antigen genes are simple to detect, allowing studies to be done in many laboratories and transplant centres. Many forms of DNA polymorphism detection are now available, allowing even modest laboratories to mount studies of their own. Despite these advances, studies in SCT have a number of problems relating to the complex clinical situation that they study; issues of study design and data interpretation in transplant studies are complex and challenging and are the main limiting factors, which inhibit progress in confirming genetic features which influence the success of SCT.