Inhibition of human macrophage colony formation by interleukin 4.

We investigated the effects of human rIL-4 on in vitro hematopoiesis. A profound inhibition of macrophage colony formation by IL-4 was observed, whereas colony growth of other lineages was not affected. Inhibition of macrophage colony growth was not restricted to GM-CSF-induced colony growth but was also present in cultures stimulated with M-CSF. This inhibition was not only observed in cultures of light density bone marrow cells, but also in cultures of monocyte- and T lymphocyte-depleted bone marrow cells. Since a similar inhibition was observed in cultures of CD34+HLA-DR+-enriched bone marrow cells, a direct action of IL-4 on monocyte-committed progenitor cells is suggested.

Interleukin 6 is a permissive factor for monocytic colony formation by human hematopoietic progenitor cells.

Since monocytes and macrophages that arise during the culture of bone marrow progenitor cells are potential sources of interleukin 6 (IL-6), we investigated whether auto- or paracrine production of this factor is involved in colony formation by normal hematopoietic progenitor cells. We added a polyclonal anti-IL-6 antiserum and a monoclonal anti-IL-6 antibody to cultures of monocyte- and T cell-depleted bone marrow cells. Colony formation was stimulated with granulocyte/monocyte-colony-stimulating factor (GM-CSF), monocyte-CSF, or IL-3. Addition of anti-IL-6 antibody resulted in decreased numbers of monocytic colonies to 40-50% of control values, whereas the numbers of granulocytic colonies were not altered. The inhibitory effect was preserved in cultures of CD34(+)-enriched bone marrow cells. As a second approach, we added a monoclonal antibody directed against the IL-6 receptor to cultures of monocyte- and T cell-depleted bone marrow cells. This antibody almost completely inhibited the growth of monocytic colonies, again without decreasing the number of granulocytic colonies. Finally, the importance of IL-6 in monocytopoiesis was demonstrated in serum-deprived bone marrow cultures: addition of exogenous IL-6 to cultures stimulated with GM-CSF resulted in increased numbers of monocytic colonies. Our results indicate that the permissive presence of IL-6 is required for optimal monocytic colony formation by bone marrow progenitor cells.

Production of tumor necrosis factor-alpha by normal and malignant B lymphocytes in response to interferon-alpha, interferon-gamma and interleukin-4.

Since autocrine stimulation by tumor necrosis factor-alpha (TNF alpha) may be implicated in the proliferation of normal and malignant B cells, we measured the production of TNF alpha protein by these cells in response to various B-cell stimulatory agents. Purified malignant and non-malignant B lymphocytes were incubated with interleukin-4 (IL4), interferon-alpha (IFN alpha) and IFN gamma, and the supernatants were tested for the production of TNF alpha using an enzyme-linked immunosorbent assay (ELISA). Chronic lymphocytic (CLL) and prolymphocytic (PLL) leukemia cells produced low amounts of TNF alpha, irrespectively of the addition of inducers. Normal B lymphocytes (tonsillar and blood) produced TNF alpha, but the level was not influenced by any of the inducers tested. Hairy cell leukemia (HCL) cells produced TNF alpha in the absence of stimuli and this production was markedly enhanced by addition of IFN alpha or, to a lesser extent, by IFN gamma and IL4. These results contradict the hypothesis that IFN alpha exerts its therapeutic action in HCL by inhibition of autocrine TNF alpha production.

Inhibitory effect of interleukin-4 on the proliferation of acute myeloid leukemia cells with myelo-monocytic differentiation (AML-M4/M5); the role of interleukin-6.

Since interleukin-4 (IL-4) specifically inhibits monocytic colony formation in human bone marrow cultures, we investigated whether a similar inhibition could be observed in cultures of optimally stimulated acute myeloid leukemia cells with myelomonocytic differentiation (AML-M4/M5). Sensitivity to IL-4 was tested in 19 cases of AML-M4/M5, using both a 3H-thymidine incorporation assay and a clonogenic assay. Proliferation was stimulated with a combination of IL-3, granulocyte-monocyte colony-stimulating factor (GM-CSF), and conditioned medium from phytohemagglutinin-stimulated leukocytes (PHA-CM). In 13 out of 14 evaluable cases, IL-4 inhibited 3H-thymidine incorporation; stimulation was seen in one case. Using a clonogenic assay, IL-4 inhibited colony formation in all evaluable cases (n = 7). Addition of IL-6 did not alter the observed inhibition by IL-4 in 9 out of 10 cases tested. We conclude that IL-4 inhibits the proliferation of optimally stimulated AML-M4/M5 cells in most cases tested, and that this effect is not generally caused by inhibition of autocrine IL-6 production.

Serum monocyte colony-stimulating factor, erythropoietin and interleukin-6 in relation to pancytopenia in hairy cell leukemia.

In patients with hairy cell leukemia (HCL), we measured serum levels of monocyte colony-stimulating factor (M-CSF), interleukin-6 (IL-6), and erythropoietin during various degrees of pancytopenia characteristic for this disease. Serial sera from 12 HCL patients during various stages of the disease were analyzed. No correlation was found between the levels of M-CSF or IL-6 and the numbers of circulating monocytes or platelets, normal values of M-CSF (4 to 10 mg/l), and IL-6 (3-50 U/ml) being detected during all stages of the disease. In contrast, erythropoietin levels were inversely related with the hemoglobin concentration (r = -0.79), indicating the presence of a normal feedback mechanism for this factor in patients with HCL.

Characterization of a New Human B Cell Line (Bonna-12) with Trisomy 9 and Trisomy 12 Chromosomal Abnormality.

A new EBV positive human B-cell line, BONNA-12 was established from splenic cells of a patient with a hairy cell leukemia (HCL). BONNA-12 cells grew spontaneously and formed colonies in semisolid media. Although the BONNA-12 cell line was identical with the patient's spleen cells by HLA analysis and Southern blot examination of minisatellite DNA patterns, the immunoglobulin heavy and light chain rearrangement patterns differed from the original HCL. Cytogenetic analysis of the BONNA-12 cell line demonstrated in the major cell clone a 47, X, -Y, +9, +12 karyotype. Trisomy 12 is a characteristic abnormality in chronic lymphocytic leukemia that also rarely occurs in HCL. The BONNA-12 cell line is of potential value in the study of trisomy 12 in chronic B cell malignancies.

Differential stimulatory and inhibitory effects of interleukin 4 on granulocytic and monocytic colony formation in human bone marrow cultures.

Both stimulatory and inhibitory effects of interleukin (IL) 4 on myelopoiesis have been described. In this paper we further define the specificity of these effects. IL-4 was added to cultures of bone marrow cells in which colony formation was stimulated with several colony-stimulating factors (CSFs): monocyte CSF (M-CSF), granulocyte CSF (G-CSF), IL-3, IL-5 and conditioned medium from phytohemagglutinin-stimulated peripheral blood cells (PHA-CM). Inhibition of monocytic colony formation by IL-4 was observed in cultures that were stimulated with IL-3 or with PHA-CM, similar to the inhibition in M-CSF- or GM-CSF-stimulated cultures. The enhancement of granulocytic colony formation by IL-4 was restricted to G-CSF-induced colony growth. No enhancement was observed in cultures that were stimulated with IL-5 or with PHA-CM from which the G-CSF was neutralized by anti-G-CSF antibodies. Both the inhibiting and enhancing effects of IL-4 were preserved in cultures that were stimulated with concentrations of CSF that exceeded more than tenfold the plateau concentrations. Enhancement of granulocytic and inhibition of monocytic colony formation by IL-4 occurred simultaneously in cultures stimulated with PHA-CM or with a combination of G-CSF and M-CSF. In summary, we show that the inhibiting effect of IL-4 on monocytic colony formation is independent of the growth factor used, whereas the stimulatory effect of IL-4 on granulocytic colony formation is restricted to G-CSF-induced cultures. Simultaneous occurrence of both effects results in preferential growth of granulocytes.

Induction of CD11a/leukocyte function antigen-1 and CD54/intercellular adhesion molecule-1 on hairy cell leukemia cells is accompanied by enhanced susceptibility to T-cell but not lymphokine-activated killer-cell cytotoxicity.

Some B-cell neoplasms, including hairy cell leukemia (HCL), lack expression of the adhesion molecule leukocyte function antigen-1 (LFA-1/CD11a). Additionally, HCL cells express relatively low amounts of intercellular adhesion molecule-1 (ICAM-1/CD54) and may therefore be an inappropriate target for recognition by T cells or lymphokine-activated killer (LAK) cells. We tested whether these molecules were inducible on HCL cells and if induction would lead to enhanced susceptibility to lysis by LAK cells or cytolytic T cells. CD11a expression was induced by incubation with interferon-alpha (IFN-alpha) or interleukin-4. CD54 was induced by culturing the cells irrespectively of the addition of cytokines. Expression of CD11a and CD54 did not enhance susceptibility to either autologous or allogeneous LAK cells. However, induction of these adhesion molecules was accompanied by enhanced susceptibility to lysis by cytotoxic T lymphocyte clones. This lysis could be reversed by the addition of anti-CD11a and anti-CD54 antibodies. Finally, we monitored the expression of CD11a and CD54 on HCL cells from patients during IFN-alpha therapy. In one of four patients monitored, we observed rapid in vivo induction of CD11a and CD54 on the leukemic cells during IFN-alpha therapy. These studies provide a model for studying immunosurveillance in HCL.

Interleukin 4 down-regulates the expression of CD14 and the production of interleukin 6 in acute myeloid leukemia cells.

On normal monocytes, interleukin 4 (IL-4) down-regulates the production of several proteins that are produced in response to bacterial cell wall lipopolysaccharides (LPS), among others IL-6. In addition, IL-4 was shown to down-regulate the expression of the monocytic differentiation marker CD14, recently identified as a receptor for LPS. Since (autocrine) IL-6 is possibly involved in the proliferation and differentiation of acute myeloid leukemia cells with myelomonocytic differentiation (AML-M4/M5), we studied the effects of IL-4 on IL-6 production and CD14 expression by these cells. We found that IL-4 down-regulates both the expression of CD14 (n = 6) and the production of IL-6 (n = 9) in AML cells. Using Northern blot analysis, we found that IL-4 down-regulates the level of steady-state mRNA for both CD14 (two of three cases tested) and IL-6 (three cases tested).