CD4 and hand, foot and mouth disease: The complications of brain stem encephalitis and pulmonary edema caused by EV71 virus in HFMD patients are always accompanied by significant increases in serum interleukin (IL)-13, IL-10, IL-8, interferon gamma (IFN-γ), monocyte chemotactic factor 1 cytokine, natural killer (NK) cells, CD4+ T lymphocytes, and CD8+ T lymphocytes [18].