Major Histocompatibility Complex (MHC) is part of genome which plays a essential role in immune response to protein antigens and located on the short arm of the six chromosome. In human beings, it named HLA. HLA is divided three areas based on its tissue distribution and function of its building that is including HLA class I (locus A, B and C), class II (DQ, DR and DP) and class III. The association between the genes of the HLA and many diseases such as Behçet disease, myasthenia gravis, multiple sclerosis, HIV, HTLV, malaria, Mucosal Leishmaniasis and Toxoplasma gondii has been known in epidemiologic and demographic studies. Understanding the specific HLA alleles associated with susceptibility or resistance to a disease can be effective in produce and development of drugs, identifying the populations at high risk or resistance to a disease as well as in planning and prevention.