CXCL1 and major depressive disorder: We found that older adults with MDD have significantly elevated mRNA expression of IL-1β (p = 0.001), IL-2 (p = 0.029), IL-8 (p = 0.020), IL-10 (p = 0.036), IL-13 (p = 0.025), TNF- α (p = 0.0004), and CXCL-1 (p = .018) when compared to controls (Figure 3).