COMPARISON OF THE IMMUNOGLOBULIN HEAVY-CHAIN COMPLEMENTARITY-DETERMINING REGION-3 STRUCTURE AMONG THE DNA-SEQUENCES AND THE MU-TRANSCRIPT AND GAMMA-TRANSCRIPT IN HUMAN B-LINEAGE CELLS

To study the recombinational significance of the (immunoglobulin heavy ) IgH chain gene in human B-cell development, we compared the compleme ntarity determining region (CDR)-3 sequences of the DNA and the mu-tra nscripts from human normal pre-B cells and mature B cells, and the gam ma-transcripts from bone marrow cells. The CDR-3 sequences were longer in the DNA than in the mu- and gamma-transcripts, and this was indepe ndent of whether or not the rearrangement was productive. The DLR fami ly genes were less frequently used in the mu- and gamma-transcripts. W hen translated into amino acids, all CDR-3 sequences from the mu- and gamma-transcripts were productive, although 26.2% of the DNA sequences had stop codons in the D element and/or frameshifts of the ts. The CD R-3 of the productive DNA sequences in pre-B cells frequently (26.6%) contained at least three continuous hydrophobic amino acids, which wer e mainly coded by the DLR and DXP family genes at the third reading fr ame. However, such motifs were rare in the mu-transcripts of pre-B (7. 7%) and mature B cells (3.9%), and in the gamma-transcripts of bone ma rrow cells (1.1%) as well as in the DNA of mature B cells (10.4%). The se findings suggested that the length and/or hydrophobicity of the IgH CDR-3 might play a role in the selection mechanisms of B-cell develop ment.