Peripheral toll-like receptor expression indicates distinct innate immune signatures in schizophrenia spectrum and mood disorders: A systematic review and meta-analysis.
Julia Karska, Szymon Kowalski, Kamila Rudy et al.
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In 30 seconds
This systematic review and meta-analysis examined peripheral blood mRNA expression of TLR1–TLR10 in schizophrenia spectrum disorders (SSD) and mood disorders compared with healthy controls. Across 26 studies, involving 678 people with SSD, 523 with mood disorders, and 1182 controls, random-effects analyses found distinct patterns of elevated expression. In SSD, TLR4, TLR8, and TLR10 were significantly increased (g = 0.26 - 0.31, p FDR < 0.05); in mood disorders, TLR2, TLR5, and TLR6 were increased (g = 0.23 - 0.32, p FDR < 0.05).
Key findings
- In SSD, TLR4, TLR8, and TLR10 expression was significantly elevated versus healthy controls (g = 0.26 - 0.31, p FDR < 0.05).
- In mood disorders, TLR2, TLR5, and TLR6 expression was significantly elevated versus healthy controls (g = 0.23 - 0.32, p FDR < 0.05).
- The meta-analysis included 26 studies: 678 individuals with SSD, 523 with mood disorders, and 1182 healthy controls.
Why it matters
The differing TLR expression patterns suggest that peripheral innate immune activation may not be uniform across psychiatric diagnostic groups. This supports investigating immune signatures as a way to characterize biological heterogeneity, while the findings remain associations and do not establish mechanisms or clinical utility. The authors identify longitudinal, experimental, and multi-omics research as necessary to clarify these patterns.
What to keep in mind
The findings synthesize peripheral mRNA measurements and do not establish causal mechanisms; the authors call for longitudinal and experimental studies to provide further mechanistic insight.