Alternative adaptive immunity strategies: coelacanth, cod and shark immunity

Area of Science:

• * Evolutionary immunology
• * Comparative genomics
• * Vertebrate adaptive immunity

Background:

• * High throughput sequencing enables deep investigation of non-model species genomes and transcriptomes.
• * Adaptive immune gene evolution in gnathostomes reveals unexpected features in fish.
• * Understanding these systems provides insights into vertebrate immune evolution.

Purpose of the Study:

• * To review the adaptive immune systems of the coelacanth, elephant shark, and Atlantic cod.
• * To understand the evolutionary implications of immune gene variations in these species.
• * To highlight adaptive strategies in fish immune systems.

Main Methods:

• * Review of existing genomic and transcriptomic data.
• * Comparative analysis of immune gene repertoires.
• * Focus on key species: coelacanth, elephant shark, and Atlantic cod.

Main Results:

• * Coelacanths lack Immunoglobulin M (IgM) but possess IgD/W loci.
• * Elephant sharks exhibit a lack of certain T cell-related immune genes, suggesting primordial TH1-like cells.
• * Atlantic cod lack a functional Major Histocompatibility Complex II (MHC II) but show expansion in MHC I, Toll-like receptors, and antimicrobial peptides.

Conclusions:

• * Fish species display unconventional adaptive immune systems.
• * Loss of immune genes is compensated by evolutionary adaptations.
• * These strategies ensure effective immune responses against pathogens.