TNF and hand, foot and mouth disease: Therefore, the objective of this study was to determine the risk factors of severe HFMD and to assess the relationship of T cell-related serum inflammatory cytokine levels, including interleukin (IL)-4, IL-6, IL-10, IL-17, interferon (IFN)-γ and tumor necrosis factor (TNF)-α, with the progression of HFMD and its severity.