LYMPHOID SUBSETS IN ACUTE MYELOID LEUKEMIAS - INCREASED NUMBER OF CELLS WITH NK PHENOTYPE AND NORMAL T-CELL DISTRIBUTION

Natural killer (NK) and T subsets were analyzed with appropriate dual labeling by flow cytometry in peripheral blood (PB) (66 cases) and bon e marrow (BM) (55 cases) from patients with de novo AML in order to de termine: (a) their distribution at diagnosis, (b) the correlation betw een PB and BM in NK subpopulations, (c) their relationship with the cl inical and hematological disease characteristics, and (d) the changes occurring upon achieving complete remission (CR). NK cells defined by the expression of CD56 in the absence of CD3 were significantly increa sed at diagnosis and their levels in PB correlated with those of BM. B y contrast, NK subsets defined by CD16 expression (CD16+ CD2+ and CD16 + CD2- NK-cell subsets) as well as T lymphocytes with NK activity (CD5 6+ CD3+), although increased in PB, displayed normal levels in BM. An additional observation of interest was the expansion of an immature NK population lacking CD16 Ag expression (CD56+ CD16-). AML cases were d ivided into two groups according to the absolute number of NK cells in PB; patients with the highest levels showed an increased proportion o f blast cells in PB (p = 0.01), monocytic subtypes (p = 0.03), and exp ression of CD11b, CD14, and CD4 antigens (p = 0.05). Infections at dia gnosis were not related to the level of NK cells. In 19 patients who a chieved complete remission the number of CD56+ CD3- cells tended to be reduced to within the normal range. Other T-cell populations, includi ng the CD4 naive and memory cells, were also explored, their distribut ion being normal in the PB of AML patients. By contrast, the cytotoxic subset CD8+/CD57+ was significantly increased (p < 0.001). These data point to the existence of marked alterations of NK cells in AML patie nts, possibly reflecting a host-tumor immunological interaction.