Transcriptome analysis of immune genes in peripheral blood mononuclear cells of young foals and adult horses.
Authors: Tallmadge Rebecca L, Wang Minghui, Sun Qi, Felippe Maria Julia B
Journal: PloS one
Summary
# Editorial Summary: Immune Gene Expression in Young Foals Researchers used transcriptome analysis to characterise how immune gene expression differs between neonatal foals and adults, examining peripheral blood mononuclear cells at day 1, day 42, and in mature horses to understand the natural developmental trajectory of equine immunity. The study identified striking patterns: newborn foals displayed robust innate immunity genes (antimicrobial proteins, pathogen recognition receptors, and T cell receptor delta chains), whilst by day 42 adaptive immune genes had significantly upregulated, including B and T cell receptor diversity genes, natural killer receptors, and complement factors—a shift continuing into adulthood where B cell immunity became the dominant biological process. Critically, day 1 foals showed markedly suppressed TLR3 (toll-like receptor 3) expression alongside elevated immunosuppressive genes (IL27, SIRL-1, SIRP-α), a combination that likely explains their heightened pathogen susceptibility despite active innate responses. These findings suggest the neonatal foal immune system operates under a form of active immune suppression rather than simple immaturity, which has significant implications for vaccination timing, infection risk windows, and strategies to enhance early immune competence in young stock. Understanding this progression from innate to adaptive dominance provides a molecular foundation for optimising management practices and may guide development of improved neonatal health interventions.
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Practical Takeaways
- •Neonatal foals (day 1) have naturally suppressed innate immune responses with low TLR3 expression, which may explain their increased pathogen susceptibility and reduced early vaccine responsiveness
- •Significant immune maturation occurs between day 1 and day 42, suggesting vaccination timing and neonatal disease prevention strategies should account for this developmental window
- •Understanding the natural progression from innate to adaptive immunity in foals can help optimize colostrum management, vaccination protocols, and infection control in neonatal populations
Key Findings
- •Day 42 foals showed 897 genes with ≥2-fold higher expression than day 1 foals, including B/T cell receptors, NK cell receptors, and adaptive immunity genes
- •Day 1 foals showed 1,383 genes with higher expression than day 42 foals, predominantly innate immunity genes including antimicrobial proteins and pathogen recognition receptors
- •Day 1 foals had markedly low TLR3 expression and high IL27, IL13RA1, IREM-1, SIRL-1, and SIRPα expression suggesting neonatal immune suppression mechanisms
- •Immune gene expression progresses from innate-dominant in early life to adaptive-dominant by day 42, with overlaid immunosuppressive genes in neonatal phase