Polymorphism and complexity of the human DC and murine I‐A alpha chain genes.

A cDNA clone encoding the human B cell alloantigen DC alpha chain (pDCH1) has been used to analyse the structure of the human and murine major histocompatibility complexes by the DNA filter hybridization technique. The pDCH1 probe hybridizes to a single DNA sequence present on chromosome 17 in the mouse genome. A restriction enzyme polymorphism enables us to map this sequence to the I‐A subregion. Extensive restriction enzyme polymorphism detected in HLA‐DR homozygous typing cells is reminiscent of the DR/MT linkage disequilibrium groups, suggesting that the pDCH1 probe could be useful for haplotype typing in the human population. The HLA‐DR region appears more complex than the I region since a second DC‐like hybridizing sequence is detected in the human genome in these experiments.