Mouse immunoglobulin heavy chains are coded by multiple germ line variable region genes.

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Immunoglobulins (antibodies) are crucial for adaptive immunity.
• The variable region of immunoglobulin heavy chains determines antigen-binding specificity.
• Myeloma proteins provide a source for studying immunoglobulin structure and diversity.

Purpose of the Study:

• To analyze the sequence diversity of the N-terminal 20 residues of mouse immunoglobulin heavy chains.
• To infer the number of germ line genes encoding these variable regions.
• To correlate sequence variation with hapten-binding specificities.

Main Methods:

• Comparative sequence analysis of N-terminal 20 residues from 13 BALB/c mouse myeloma heavy chains.
• Comparison with 15 heavy chains from existing literature.
• Analysis of sequence patterns and clustering into sets and subsets.

Main Results:

• Sixteen of 28 heavy chain sequences exhibited differences.
• Proteins clustered into four major sets, with the largest set further divided into at least five subsets.
• Sequence diversity suggests a minimum of eight germ line genes for mouse heavy chain variable regions.
• Distinct amino acid sequences correlated with differing hapten-binding specificities.

Conclusions:

• The variable region of mouse immunoglobulin heavy chains is highly diverse.
• This diversity is likely encoded by at least eight germ line genes.
• Specific amino acid sequences within the heavy chain variable region are critical for determining hapten specificity.