Experimental evolution of immunological specificity.

Area of Science:

• Evolutionary biology
• Immunology
• Invertebrate biology

Background:

• Adaptive immunity is known for memory and specificity.
• Innate immune systems, including invertebrate immune priming, can also exhibit memory.
• The evolutionary adaptability of immune priming specificity remains largely unexplored.

Purpose of the Study:

• To investigate the evolution of immune priming specificity in the invertebrate model organism, *Tribolium castaneum*.
• To determine if natural selection can rapidly increase the specificity of innate immune priming.
• To identify the molecular mechanisms underlying changes in immune priming specificity.

Main Methods:

• Controlled evolution experiment selecting for specific or unspecific immune priming in *Tribolium castaneum* beetles.
• Exposure to various bacteria (*Pseudomonas fluorescens*, *Lactococcus lactis*, and *Bacillus thuringiensis* strains) for priming and challenge.
• Transcriptomic analysis to compare gene expression profiles between evolved populations.
• Correlation analysis between immune gene expression and survival probability.

Main Results:

• Immune priming specificity did not universally increase in selected lines; it varied depending on the specific bacterium used.
• The entomopathogen *Bacillus thuringiensis* elicited the strongest priming effect.
• Transcriptomic differences revealed the involvement of immune, metabolic, and transcription-modifying genes.
• The induction strength of specific immune genes predicted survival rates.

Conclusions:

• High specificity of innate immune priming can evolve rapidly for certain bacterial species in invertebrates.
• Evolutionary changes in immune priming specificity are likely driven by alterations in the regulation of immune genes.
• These findings highlight the dynamic and adaptable nature of innate immune memory.