Human immunoglobulin D segments: isolation of a new D segment and polymorphic deletion of the D1 segment.

We have isolated and identified a new human germline D segment which is not physically linked to the known D cluster. The nucleotide sequence of the new D segment was highly homologous with the known D segments. Frequent polymorphic deletion of the D1 segment was found in the Japanese population. Nucleotide sequences surrounding the deletion indicate that homologous recombination is likely to be responsible for the deletion of the D1 segment.