Natural killer cell immunodeficiency in patients with chronic myelogenous leukemia. III. Defective interleukin-2 production by T-helper and natural killer cells.

Even though they possess normal to increased numbers of circulating natural killer (NK) cells, patients with chronic myelogenous leukemia (CML) have a functional NK-cell deficiency which is restorable in vitro in the presence of recombinant IL-2. We therefore measured the level of IL-2 production by both T-helper and NK cells from CML patients as compared to normal controls using PHA-stimulated peripheral blood mononuclear cells (PBMs) as well as FACS-sorted CD4+ (OKT4+) lymphoid cells and FACS-sorted CD16+ (B73.1+) lymphoid cells. Peripheral blood mononuclear cells from CML patients demonstrated markedly defective IL-2 production as compared to normal controls (4.0 +/- 1.6 and 5.9 +/- 1.4 units/ml after 24 hr of 5 and 10 micrograms/ml PHA stimulation as compared with 40.7 +/- 10.3 and 69.3 +/- 15.1 units/ml for normal subjects). In addition to the decreased relative percentage of CD4+ (OKT4+) lymphoid cells in CML patients, FACS-sorted CD4+ (OKT4+) cells also demonstrated a significant defect in IL-2 production, (10.8 +/- 3.6 units/ml as compared to 39.0 +/- 5.8 units/ml after 24 hr stimulation with 10 micrograms/ml PHA). FACS-sorted CD16+ (B73.1+) lymphoid cells from CML patients also demonstrated significantly decreased IL-2 production after 24 hr incubation with increasing concentrations of PHA or with the NK-sensitive target K562 as compared to normal controls. Defective IL-2 production by PBMs, CD4+ (OKT4+), and CD16+ (B73.1+) cells from CML patients was also evident after 48 hr of PHA stimulation. Although the percentages of both T4+2H4+ and T4+4B4+ subsets are significantly decreased in CML patients, CML patients have normal ratios of T4+4B4+/T4+2H4+ subsets as compared to normal controls. These and previous results support the hypothesis that decreased IL-2 production by both T-helper and NK cells from CML patients may be mechanistically related to the observed NK-cell immunodeficiency in CML patients.