The continuous, in vivo infusion of low-dose IL-2 selectively expands the absolute number of human natural killer (NK) cells after 4-6 weeks of therapy. The mechanism responsible for this expansion is unknown and was examined in this study. NK cells cultured at low concentrations of IL-2, comparable to those found during in vivo therapy, proliferate for 6 days and then exit the cell cycle. However, NK cells in vivo did not traverse the S/G(2)/M phase of the cell cycle during low-dose IL-2 therapy. Low concentrations of IL-2 delay programmed cell death of NK cells but have the same effect on resting T cells that do not expand in vivo. When CD34(+) bone marrow hematopoietic progenitor cells are cultured for 21 days with low concentrations of IL-2, they differentiate into CD56(+)CD3(-) NK cells, not T cells. Thus, the selective expansion of human NK cells during continuous in vivo infusion of low-dose IL-2 likely results from enhanced NK-cell differentiation from bone marrow progenitors, combined with an IL-2-dependent delay in NK-cell death, rather than proliferation of mature NK cells in the periphery.

The administration of low dose interleukin-2 (IL-2) results in a selective expansion of natural killer (NK) cells in vivo, and promotes the differentiation of NK cells from hematopoietic precursor cells in vitro. We have previously shown that stem cell factor (SCF ), the ligand to the c-kit tyrosine kinase receptor, enhances IL-2-induced NK cell proliferation and differentiation in vitro. Here, we investigated the effects of SCF plus IL-2 delivered to mice in vivo. Eight-week-old C57BL/6 mice were treated with a continuous subcutaneous infusion of IL-2 (1 x 10(4) IU/d) plus a daily intraperitoneal dose of SCF (100 microg/kg/d), IL-2 alone, SCF alone, or vehicle alone for 8 weeks. The in vivo serum concentration of IL-2 ranged between 352 +/- 12.0 pg/mL and 606 +/- 9.0 pg/mL, achieving selective saturation of the high affinity IL-2 receptor, while the peak SCF serum concentration was 296 +/- 13.09 ng/mL. Alone, the daily administration of SCF had no effect on the expansion of NK cells. The continuous infusion of IL-2 alone did result in a significant expansion of NK1.1+CD3- cells compared to mice treated with placebo or SCF. However, mice treated with both SCF and IL-2 showed an increase in the absolute number of NK cells that was more than twofold that seen with IL-2 alone, in the spleen (P </= .005), bone marrow (P </= .025), and blood (P < .05). NK cytotoxic activity against YAC-1 target cells was significantly higher for mice treated with SCF plus IL-2, compared to mice treated with IL-2 alone (P </= .0005). Interferon-gamma (IFN-gamma) production in cytokine-activated splenocytes was also greater for the SCF plus IL-2 group, over IL-2 treatment alone (P </= .01). The effect of SCF plus IL-2 on NK cell expansion was likely mediated via NK cell precursors, rather than mature NK cells. In summary, we provide the first evidence that SCF can significantly enhance expansion of functional NK cells induced by the prolonged administration of low dose IL-2 in vivo. Since the NK cell is a cytotoxic innate immune effector and a potent source of IFN-gamma, this therapeutic strategy for NK cell expansion may serve to further enhance innate immune surveillance against malignant transformation and infection in the setting of cancer and/or immunodeficiency.

Human natural killer (NK) cells are bone marrow (BM)-derived CD2+CD16+CD56+ large granular lymphocytes (LGL) that lack CD3 yet contain the T-cell receptor zeta-chain (zeta-TCR). NK cells provide requisite interferon-gamma (IFN-gamma) during the early stages of infection in several experimental animal models. A number of studies have shown that human CD3-CD56+ NK cells can be obtained from BM- derived CD34+ hematopoietic progenitor cells (HPCs) cultured in the presence of interleukin-2 (IL-2) and an allogeneic feeder cell layer, or IL-2 and other hematopoietic growth factors such as the c-kit ligand (KL). The failure to detect the IL-2 gene product within the BM stroma and the presence of NK cells in IL-2-deficient mice suggested that cytokines other than IL-2 may participate in NK cell differentiation from HPCs in vivo. IL-15 is a cytokine which, while lacking any sequence homology in IL-2, can activate cells via the IL-2 receptor. Here we show that human BM stromal cells express the IL-15 transcript, and supernatants from long-term BM stromal cell cultures contain IL-15 protein. In vitro, CD3-CD56+ NK cells can be obtained from 21-day cultures of CD34+ HPCs supplemented with IL-15 in the absence of IL-2, stromal cells, or other cytokines. The addition of the KL to these cultures had no effect on the differentiation of the CD3-CD56+ cytotoxic effector cells, but greatly enhanced their expansion. The majority of these cells lack CD2 and CD16, but do express zeta-TCR. Similar to NK cells found in peripheral blood, the CD2-CD16-CD56+ NK cells grown in the presence of IL-15 were found to be potent producers of IFN-gamma in response to monocyte-derived cytokines. Thus IL-15, like KL, appears to be produced by BM stromal cells. IL-15 can induce CD34+ HPCs to differentiate into CD3-CD56+ NK cells, and KL can amplify this. Therefore, IL-15 may be a physiologically relevant ligand for NK cell differentiation in vivo.

An unbalanced translocation between chromosomes 1 and 16, der(16)t(1;16), resulting in trisomy 1q and loss of genetic material from 16q, has been thus far suggested to constitute a nonrandom secondary abnormality in two types of closely related solid tumors - Ewing sarcoma and peripheral primitive neuroepithelial tumor (PNET). We report on three cases of soft tissue tumors, a myxoid liposarcoma, a PNET and a rhabdomyosarcoma, and four cases of hematologic disorders, two acute lymphoblastic leukemias (ALL), an acute mixed leukemia and a refractory anemia, that in addition to primary chromosome abnormalities displayed the presence of the der(16)t(1;16). All three cases of acute leukemia were Philadelphia (Ph) chromosome-positive and all displayed both lymphoid and myeloid antigens. Our results and review of the literature indicate that the occurrence of der(16)t(1;16) is not limited to Ewing sarcoma and PNET, but that acquisition of this abnormality may represent a more general pathway of clonal evolution in several different tumor types including Ph chromosome-positive ALL, myxoid liposarcoma, rhabdomyosarcoma, breast cancer, endometrial adenocarcinoma, myelodysplastic syndromes, acute myeloid leukemia, retinoblastoma, and Wilms' tumor.

Cytogenetic analysis was performed after short-term tissue culture of a thecoma of the ovary. Trisomy of chromosome 12 was revealed as the sole chromosome abnormality. This is the first report of a chromosomal aberration in thecoma of the ovary.

Cytogenetic analysis carried out in 209 patients with reproduction failure demonstrated chromosomal aberrations in 6 married couples. In 5 of these cases balanced translocations were found, and in one case 45,X/46,XX cell mosaicism was present. The proportion of abnormal karyotypes in the group was 5.7% per one couple and was only slightly lower than the mean frequency of chromosomal aberrations calculated by the authors in cases of reproduction failures diagnosed in other cytogenetic laboratories in Poland-6.7%. The identical frequency of aberrations in married couples with a history of 2 or 3 or more abortions indicates the necessity of carrying out cytogenetic investigations already after two spontaneous abortions.