TNF and major depressive disorder: Similarly, the expression of several genes previously implicated in neurological and inflammatory disorders, including TNF, were found to be upregulated in the peripheral blood mononuclear cells of a combined sample of depressed MDD and BD participants.14 Further, Pandey et al.13 found that the mRNA expression of IL-1, IL-6 and TNF, as well as their receptors, IL-1R1, IL-1RA and TNFR1 was significantly greater in the lymphocytes from BD patients than those of healthy controls.