Lack of information on unique diseases has led to research on human components associated with disease defense such as the major histocompatibility complex (MHC), also known as the human leukocyte antigen (HLA). This genetic complex produces three classes of MHC receptors in humans, MHC/HLA I, II, and III, located on the cell membrane. MHC is a highly polymorphic gene complex with high linkage disequilibrium. Molecular changes and mutations on units of the MHC increase susceptibility for disease. These findings led to procedures which purposely induced changes on the MHC to prove its association with disease susceptibility. Analyzing and sequencing the genome of the HLA gene region is an important part of understanding the MCH, but sequencing can be difficult due to its high polymorphism trait. These issues led to faster, more efficient, and cheaper methods for sequencing not just the HLA but any gene region. Technology such as mass spectrometry is also facilitating characterization of HLAs, and finding disease correlations. With these advances in technology, a source for various diseases can be found.