CD4 and myalgic encephalomeyelitis/chronic fatigue syndrome: Among the immunological alterations presented by ME/CFS patients, there is reduced cytotoxic response by T lymphocytes and natural killer cells (NKs) [1, 35, 44, 357], reduced T-cell responses to mitogens and other specific antigens with decreased activation [1, 35, 358], deficient EBV-specific B- and T-cell response [21], increased Th2 response (especially IL-10) [35, 36, 38, 41, 46, 359], increased regulatory T cells (CD4+CD25+FoxP3+) [359], and increased IFN-γ levels [359].