Moreover, MDD and BD are accompanied by activation of the immune-inflammatory response system (IRS) reflected by alterations of acute phase proteins (APPs) (e.g. C-reactive protein and albumin) and activation of cell-mediated immunity as shown by increased interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-1β, IL-2, interferon (IFN)-γ, soluble IL-2 receptor (sIL-2R), sCD8, high levels of activated T cells such as CD25+ and HLA-DR+) [11]. Here, TNF is linked to major depressive disorder.