The HLA-A, -B, -C, and -DRB1 loci are the most polymorphic genes in the entire human genome. The number of distinct HLA-A, -B, -C, -E, -F, -G, -DRA, -DRB1, -DQA1, -DQB1, -DPA1, -DPB1, MICA, and MICB proteins collectively encoded by all known alleles at the corresponding MHC loci is indicated. Data were taken from http://www.ebi.ac.uk/imgt/hla/stats.html; accessed February 13, 2012.