took sigmoid colonic mucosal biopsies from patients with and without PD and found decreased SCFA-producing bacteria, increased TLR4 and CD3+ T cell mRNA expression, increased TLR4+ cells and CD3+ T cells, and increased TLR4 downstream signaling products (proinflammatory cytokines) in the lamina propria of PD patients compared to healthy controls. This evidence concerns the gene TLR4 and Parkinson disease.