Megabase scale restriction fragment length polymorphisms in the human major histocompatibility complex.

Pulsed-field gel electrophoresis of human peripheral blood lymphocyte DNA was used to ascertain the extent of megabase restriction fragment length variation in the HLA region of human chromosome 6 and to determine whether previously reported diversity was due to experimental variation or DNA polymorphism. Polymorphism was found to predominate in the vicinity of the class II DR, class III complement, and the class I A genes and to be limited or absent near the class II DP genes, the TNF genes, and the class I B and C genes. Thus, the MHC region is characterized by both fine and large-scale structural diversity.