Cell selection strategies for making antibodies from variable gene libraries: trapping the memory pool.

Area of Science:

• Immunology and Molecular Biology
• Antibody Engineering
• Recombinant DNA Technology

Background:

• B cells from immunized animals are a source for antibody variable (V) gene libraries.
• Bacterial expression of V gene libraries allows direct antibody production and screening.
• Investigating antigen-selected B cells can optimize V gene library construction.

Purpose of the Study:

• To evaluate antigen-selected B cells as a source for heavy chain variable (VH) gene libraries.
• To compare the frequency of antigen-binding clones from different library preparation methods.
• To analyze the V gene usage and D segment diversity in antibody libraries.

Main Methods:

• Mice were immunized with (4-hydroxyl-3-nitrophenyl)acetyl (NP)-chicken gammaglobulin.
• VH gene libraries were constructed from DNA of antigen-selected splenocytes and from DNA/mRNA of unselected splenocytes.
• Libraries were expressed as Fv fragments in Escherichia coli and screened for antigen binding.

Main Results:

• Libraries from antigen-selected cell DNA and unselected cell mRNA showed significantly higher frequencies of antigen-binding clones (>50-fold increase) compared to unselected cell DNA.
• Antigen-binding clones predominantly used the V-186.2 heavy chain, consistent with primary response hybridomas.
• D segment diversity in the DNA library from selected cells suggested derivation from memory B cells.

Conclusions:

• Antigen selection of B cells is a highly effective strategy for generating enriched antibody variable gene libraries.
• Libraries derived from antigen-selected cells may represent a valuable source of antibodies, including those from memory B cells.
• This approach offers a powerful tool for antibody discovery and engineering, particularly when recent immunization is not feasible.