In Vivo Downregulation of T Helper Cell 1 Immune Responses Reduces Atherogenesis in Apolipoprotein E-Knockout Mice

Abstract

Background— A chronic immune response involving proinflammatory T helper cell 1 (Th1) lymphocyte activation occurs in the atherosclerotic lesion, but whether this activation is protective or deleterious remains unclear. Methods and Results— We modulated the immune response of the atherosclerosis-prone apolipoprotein E-deficient (apoE^−/−) mouse. Eight-week-old apoE^−/− mice were treated daily with pentoxifylline (PTX), a known inhibitor of the Th1 differentiation pathway, or PBS (control) for 4 weeks or 12 weeks. Twelve-week PTX treatment reduced atherosclerotic lesion size by 60% (P+ T cells. In vitro addition of PTX to cultured spleen cells did not modify the production of IFN-γ but increased the production of IL-10 by T cells, indicating that PTX does not suppress IFN-γ production but rather blocks Th1 polarization while promoting Th2 polarization. Conclusions— Thus, PTX protected mice from atherosclerosis by reducing the Th1 polarization of T helper lymphocytes. This study demonstrates that the Th1 immune response associated with atherosclerosis is deleterious and that a modulation of the Th1 differentiation pathway may provide a new pharmacological tool to treat this disease.