Heavy chain variable region. Multiple gene segments encode anti-4-(hydroxy-3-nitro-phenyl)acetyl idiotypic antibodies

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• The (4-hydroxy-3-nitrophenyl)acetyl (NP) hapten elicits a specific antibody response (NPb) in C57BL/6 mice.
• This NPb response is serologically divided into two main groups, with subgroups I-IV and V-VI.
• Some antibodies in subgroups I and II utilize the unmutated heavy chain variable region (VH) germline gene 186.2.

Purpose of the Study:

• To investigate the genetic basis of the NPb idiotypic response in C57BL/6 mice.
• To compare the VH gene sequences of NPb-producing antibodies with NPa-producing antibodies from BALB/c mice.

Main Methods:

• Sequencing of heavy chain complementary DNA from eight anti-NP antibody-producing hybridomas (six from C57BL/6, two from BALB/c).
• Sequence analysis and Southern blot hybridization.

Main Results:

• All sequenced antibodies showed homology, differing by approximately 80 base pairs from the 186.2 C57BL/6 germline VH gene.
• The NPb response appears to originate from several VH germline genes, some homologous to BALB/c NPa genes, potentially representing allelic forms.
• Diversity regions varied in length and composition, except for a conserved tyrosine at the first residue.
• All heavy chain joining region gene segments were expressed without mutation.

Conclusions:

• The NPb idiotypic response is generated by multiple VH germline genes, highlighting germline diversity.
• Homology between NPb and NPa genes suggests allelic variations contribute to antibody repertoire.
• Antibody diversity arises from germline repertoire, gene segment joining, and potentially somatic mutation, though joining regions appear unmutated in this study.