Intensive chemotherapy for acute myeloid leukemia differentially affects circulating T(C)1, T(H)1, T(H)17 and T(REG )cells

BACKGROUND: Several observations suggest that immunological events early after chemotherapy, possibly during the period of severe treatment-induced cytopenia, are important for antileukemic immune reactivity in acute myeloid leukemia (AML). We therefore investigated the frequencies of various T cell subsets (T(C)1, T(H)1, T(H)17) and CD25(+ )FoxP3(+ )T(REG )cells in AML patients with untreated disease and following intensive chemotherapy. RESULTS: Relative levels of circulating T(C)1 and T(H)1 cells were decreased in patients with severe chemotherapy-induced cytopenia, whereas T(H)17 levels did not differ from healthy controls. Increased levels of regulatory CD25(+ )FoxP3(+ )T cells were detected in AML patients with untreated disease, during chemotherapy-induced cytopenia and during regeneration after treatment. T(H)17 and T(H)1 levels were significantly higher in healthy males than females, but this gender difference was not detected during chemotherapy-induced cytopenia. Finally, exogenous IL17-A usually had no or only minor effects on proliferation of primary human AML cells. CONCLUSIONS: We conclude that the effect of intensive AML chemotherapy differ between circulating T cell subsets, relative frequencies of T(H)17 cells are not affected by chemotherapy and this subset may affect AML cells indirectly through their immunoregulatory effects but probably not through direct effects of IL17-A.