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Multiple evolutionary routes to immune diversification across animals.
Mizuki Taguchi1,2,3, Sébastien de La Forest Divonne1,2,3, Ryo Morimoto1,2,3
1Department of Molecular Biology, Umeå University, Umeå, 901 87, Sweden.
International Immunology
|April 15, 2026
Summary
Adaptive immunity evolved gradually across Metazoa, not abruptly in vertebrates. Comparative analysis reveals shared design principles in immune diversification and cell differentiation, suggesting multiple evolutionary strategies for immune recognition.
Area of Science:
- Comparative immunology
- Evolutionary biology
- Metazoan immunity
Background:
- Adaptive immunity, characterized by antigen receptors and lymphocyte lineages, is a hallmark of vertebrates.
- The evolutionary origins of vertebrate adaptive immunity remain unclear.
- Understanding immune system evolution requires a comparative approach across animal phyla.
Purpose of the Study:
- To examine adaptive immunity across Metazoa from a comparative perspective.
- To identify shared design principles linking molecular diversification, immune cell differentiation, and proliferation.
- To explore the evolutionary trajectory of adaptive immunity.
Main Methods:
- Review of adaptive immune architectures in jawed and jawless vertebrates.
- Survey of antigen receptor diversification mechanisms in invertebrates.
- Analysis of single-cell transcriptomics data for invertebrate immune cell diversification.
Main Results:
- Vertebrate adaptive immunity utilizes distinct molecular mechanisms (e.g., V(D)J recombination, cytidine deaminase-dependent diversification) but shares core design principles.
- Invertebrate systems demonstrate diverse antigen receptor diversification strategies independent of canonical clonal selection.
- Single-cell transcriptomics reveals complex invertebrate immune cell lineages and regulatory programs.
Conclusions:
- Adaptive immunity did not emerge suddenly but evolved as one solution among diverse immune diversification strategies.
- Understanding interactions between diversification, proliferation, and cellular organization across animal lineages is crucial for deciphering vertebrate adaptive immunity's evolution.
- Shared design principles underscore convergent evolution in immune system development.
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