cDNA clone for the heavy chain of the human B cell alloantigen DC1: strong sequence homology to the HLA-DR heavy chain.

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Abstract
A c[complementary]DNA library was constructed from a [human] B cell mRNA fraction enriched for HLA-DR sequences, and cDNA clones corresponding to sequences specifically expressed in B lymphocytes were isolated by a differential screening procedure. Analysis of these clones with probes specific for the HLA-DR H chain gene allowed the characterization of HLA-DR H chain-related sequences. One clone, pDCH1, was demonstrated to encode the DC1 H chain because the amino acid sequence predicted from its nucleotide sequence matches 8 of 9 residues available for comparison in the amino-terminal sequence of the DC1 H chain. The H chain of the DC1 alloantigen is composed of 232 amino acids and can be divided into 2 external domains, .alpha.1 (amino acids 1-87) and .alpha.2 (amino acids 88-181), a connecting peptide (amino acids 182-194), a hydrophobic transmembrane region (amino acids 195-217), and an intracytoplasmic region (amino acids 218-232). Comparison with the HLA-DR H chain reveals strong sequence homology in the 2nd external Ig-like domain (.alpha.2) and the transmembrane region. In contrast, the 1st external domain, the connecting peptide, and the intracytoplasmic region are less conserved.