Regulation of p38 MAP kinase in CD4+ lymphocytes by infliximab therapy in patients with rheumatoid arthritis

Tumor necrosis factor α (TNFα) plays a key role in the pathogenesis of rheumatoid arthritis (RA) and most patients treated with anti-TNFα agents show significant improvement in both signs and symptoms. While TNFα inhibitors rapidly reduce joint inflammation, the mechanisms by which these agents exert their long-term effects remain unclear. The p38 MAP kinase pathway is one of the signaling pathways triggered by TNFα and pharmacological inhibitors of this kinase are being developed for use in RA. Since p38 MAP kinase is involved in interferon γ (IFNγ) production by CD4+ T helper 1 (Th1) cells and a Th1 immune response has been associated with RA, we investigated whether anti-TNFα therapy could affect the activation of this signaling pathway in the CD4+ T cells of RA patients. We show that in five patients, treatment with infliximab caused a marked reduction of activated p38 MAP kinase levels in CD4+ T cells, without affecting the total levels of p38 MAPK. In contrast to T cells, infliximab therapy did not affect the levels of active p38 MAP kinase in macrophages from the same patients. The selective effect of anti-TNFα therapy on the p38 MAP kinase signaling pathway of CD4+ T cells in patients with RA suggests that prolonged benefit with these agents may be mediated by their effect on CD4+ T cells.