IL6 and obesity due to melanocortin 4 receptor deficiency: Qiao et al. 38 showed that an increase in the Lactococcus population in Peyer’s patches is associated with an obesity-prone phenotype, and was positively correlated with the levels of pro-inflammatory cytokines such as interleukin (IL)-6 and TNF-α, but negatively associated with the levels of anti-inflammatory cytokines such as IL-10.