TNF and inflammatory response: Subsequently, some studies have shown clinical evidence of bowel inflammation in PD patients for example; Devos et al. found increased expression of proinflammatory cytokines (tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), interleukin (IL)-6, and IL-1β) in PD patients using real-time PCR analysis of mRNA expression of pro-inflammatory cytokines in the ascending colon biopsies of PD patients and controls (Devos et al., 2013).