Map of the MHC showing the proposed class IV region. Physical map and organization of the human MHC and selected genes. Expressed HLA class I and class II genes (rectangles) are positioned on the horizontal meridian. Genes with putative immune function (triangles) and other genes (circles) are elevated above the horizontal meridian. A blow-up view of the proposed class IV region is shown beneath. Physical distances are approximate and derived from the sources referenced in the text, or are from unpublished data. Symbols for known genes are conventional abbreviations or are defined in the text.5 ZNF 173 and ZNF 178 are zinc finger genes that map in the vicinity of HLA-A.^6,102