Extensive polymorphism surrounding the murine Ia A beta chain gene.

Area of Science:

• Immunogenetics
• Molecular Biology
• Cell Surface Antigens

Background:

• The murine immune response-associated (Ia) antigen A beta chain is a highly polymorphic cell surface protein.
• Understanding the genetic organization of Ia antigens is crucial for studying immune responses.

Purpose of the Study:

• To clone and characterize a cDNA segment of the murine Ia antigen A beta chain mRNA.
• To investigate the gene organization and polymorphism of the murine A beta chain.

Main Methods:

• Screening of 5000 cDNA clones using filter hybridization-selection assay with rabbit heteroantiserum.
• In vitro translation to identify the A beta chain.
• Nucleotide sequencing of the 464 bp cDNA insert.
• Southern blot analysis using the cDNA clone as a probe.

Main Results:

• A cDNA clone, pIA beta-1, representing the carboxyl end of the murine A beta chain mRNA was isolated.
• The nucleotide sequence showed potential homology to human Ia beta chain cDNA.
• Southern blot analysis indicated a single A beta chain gene per haploid mouse genome.
• Significant restriction fragment length polymorphism was observed for the A beta chain gene.

Conclusions:

• The study successfully cloned and sequenced a portion of the murine Ia antigen A beta chain mRNA.
• Evidence suggests a single gene encodes the A beta chain in mice.
• High polymorphism in restriction fragments of the A beta chain gene was detected.
• The mechanisms generating A beta chain polymorphism may also contribute to restriction site polymorphism.