While TLR4 expression did not show any difference after stimulation with K. variicola, TLR2 and TLR9 mRNA expression were significantly increased in microglial cells (Fig. 4B), suggesting that TLR2 and TLR9, but not TLR4, are the microglial cell receptors that bound to K. variicola upon stimulation in line with the impact of whole PD-associated microbiome shown above. Here, TLR4 is linked to Parkinson disease.