Two forms of adaptive immunity in vertebrates: similarities and differences

Area of Science:

• Comparative immunology
• Evolution of adaptive immunity

Background:

• Jawed vertebrates utilize T-cell and B-cell receptors for antigen recognition.
• Jawless vertebrates, including lampreys and hagfish, employ variable lymphocyte receptors (VLRs) for antigen recognition, a distinct mechanism.
• VLRs achieve antigen receptor diversity through the assembly of variable leucine-rich repeat modules.

Purpose of the Study:

• To review current knowledge on the adaptive immune systems (AISs) of jawless vertebrates.
• To highlight similarities and differences between the AISs of jawed and jawless vertebrates.
• To explore the evolutionary origins of adaptive immunity.

Main Methods:

• Review of existing literature on jawless vertebrate immunology.
• Comparative analysis of adaptive immune system architectures.
• Examination of lymphocyte lineage conservation.

Main Results:

• VLRs in jawless vertebrates generate comparable diversity to gnathostome antigen receptors.
• The discovery of VLRs has reshaped understanding of adaptive immunity evolution.
• Significant commonalities exist between jawed and jawless vertebrate AISs, particularly in lymphocyte lineages.

Conclusions:

• The fundamental architecture of the AIS, including lymphocyte dichotomy, was likely established in a common vertebrate ancestor.
• Adaptive immunity in vertebrates exhibits both divergent (receptor type) and conserved (lymphocyte lineages, basic architecture) features.
• Understanding jawless vertebrate AIS provides crucial insights into the evolution of vertebrate adaptive immunity.