Exon shuffling: mapping polymorphic determinants on hybrid mouse transplantation antigens

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Major histocompatibility complex (MHC) class I molecules, such as H-2K, H-2D, and H-2L in mice, are crucial for immune responses and cell recognition.
• These transplantation antigens are highly polymorphic and possess numerous alloantigenic determinants, historically defined by antisera.
• Recent advancements with monoclonal antibodies have refined the understanding of these determinants, but structural correlation remains incomplete.

Purpose of the Study:

• To structurally map the serological determinants of mouse H-2 transplantation antigens.
• To correlate classically defined serological specificities with specific domains of the H-2 protein structure.

Main Methods:

• Molecular cloning of H-2Ld and H-2Dd genes from BALB/c mice.
• Construction of novel H-2 antigen genes by fragmenting and rejoining H-2Ld and H-2Dd genes.
• Expression of these engineered genes in mouse L cells to synthesize hybrid H-2 proteins.
• Utilizing monoclonal antibodies with defined specificities to analyze the resulting hybrid H-2 proteins.

Main Results:

• Successfully generated hybrid H-2 proteins by combining gene fragments from H-2Ld and H-2Dd.
• Mapped specific, classically defined serological specificities to distinct structural domains within the transplantation antigen protein.
• Demonstrated that polymorphic determinants, recognized by monoclonal antibodies, reside in functionally distinct regions of the H-2 protein.

Conclusions:

• Established a structure-function relationship for H-2 transplantation antigen determinants.
• Provided a framework for understanding how polymorphic determinants contribute to cell-cell interactions and immune recognition.
• Highlighted the utility of gene engineering and monoclonal antibody analysis for dissecting complex cell-surface protein functions.