IL6 and major depressive disorder: in the cecum (Bailey et al., 2011), while mental stress increases the levels of peripheral IL-6 and chemokine CCL2, and the expression of TLR3 and TLR4 in the prefrontal cortex of suicidal patients with depression, leading to hyperactivation of microglia (García Bueno et al., 2016; Park et al., 2018).