Deficiency of iPLA2β primes immune cells for proinflammation: Potential involvement in age-related mesenteric lymph node lymphoma

Abstract

Proinflammation can predispose the body to autoimmunity and cancer. We have reported that iPLA2β-/- mice are susceptible to autoimmune hepatitis and colitis. Here we determined whether cytokine release by immune cells could be affected by iPLA2β-/-deficiency alone or combined with CD95/FasL-antibody treatment in vivo. We also determined whether cancer risk could be increased in aged mutant mice. Immune cells were isolated from 3-month old male WT and iPLA2β-/- mice, and some were injected with anti-CD95/FasL antibody for 6 h. Kupffer cells (KC) or splenocytes and liver lymphocytes were stimulated in vitro by lipopolysaccharide or concanavalinA, respectively. Whole-body iPLA2β deficiency caused increased apoptosis in liver, spleen, and mesenteric lymph node (MLN). KC from mutant mice showed suppressed release of TNFa and IL-6, while their splenocytes secreted increased levels of IFNg and IL-17a. Upon CD95/FasL activation, the mutant KC in turn showed exaggerated cytokine release, this was accompanied by an increased release of IFNg and IL-17a by liver lymphocytes. Aged iPLA2β-/- mice did not show follicular MLN lymphoma commonly seen in aged C57/BL6 mice. Thus, iPLA2β deficiency renders M1- and Th1/Th17-proinflammation potentially leading to a reduction in age-related MLN lymphoma during aging.