Abstract: Rheumatoid arthritis (RA) is a systemic autoimmune disease whose main feature is persistent joint inflammation.
Toll-like receptors (TLRs) play critical roles in the activation of innate and adaptive immune responses, and
influence the activity of NF?B, a key player in chronic inflammation. We aimed at investigating the association of
TLR allelic variants with susceptibility and severity of RA through a systematic, high-throughput, analysis of TLR
genes. All coding exons and flanking regions of nine members of the TLR family (TLR1-9) were analyzed in 66
patients with RA and 30 healthy controls by next generation sequencing. We focussed on three single allelic
variants, N248S in TLR1, Q11L in TLR7 and M1V in TLR8 based on the allelic frequencies in both patient and
control populations, the predicted impact on protein function and the novelty in RA research. Analysis of these
selected variants in a larger cohort of 402 patients with RA and in 208 controls revealed no association with
susceptibility. However, the M1V allele was associated with a lower need for disease-modifying antirheumatic
drugs (DMARDs) (p =0.008) and biologic treatments (p =0.021). Functional studies showed that the M1V
variant leads to a reduced production of inflammatory cytokines, IL-1?, IL-6 and TNF?, in response to TLR8
agonists. Thus, the presence of this variant confers a significant protective effect on disease severity. These
results show for the first time the association between the M1V variant of TLR8 and reduced disease severity in
RA, which could have prognostic value for these patients.
