The antibody repertoire in evolution: chance, selection, and continuity

Area of Science:

• Immunology
• Evolutionary Biology
• Genetics

Background:

• Jawed vertebrates share genetic elements for adaptive immunity.
• Antibodies exhibit diversity through gene recombination and hypervariable regions.
• Conserved gene segments suggest evolutionary stability.

Purpose of the Study:

• To investigate the evolutionary conservation of adaptive immune system components in jawed vertebrates.
• To compare antibody structure and genetic elements across vertebrate species.
• To identify conserved features in antibody gene segments and their implications for immune function.

Main Methods:

• Comparative analysis of germline VH and VL gene segments across vertebrate species.
• Examination of conserved framework (FR2, FR3) and joining (J) segments in light and heavy chains.
• Structural modeling of shark antibody combining sites.
• Database searches for related molecules in lower deuterostomes and invertebrates.

Main Results:

• High conservation of germline VH, VL, and J segments observed across jawed vertebrates.
• Specific conserved motifs identified in light chain (FGXGT(R or K)L) and heavy chain (WGXGT(uncharged)VT JH) J segments.
• Shark antibody structures show similarities to human counterparts in framework and CDR usage.
• No significant related molecules found in invertebrates, indicating jawed vertebrate origin.

Conclusions:

• Adaptive immunity in jawed vertebrates relies on conserved genetic blueprints established over 450 million years ago.
• Despite individual antibody diversity, core structural and genetic features of the adaptive immune system are highly conserved.
• These conserved elements underscore the evolutionary significance of the jawed vertebrate immune system.