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Biomedical subjects

L Aarden

Publications and source records attributed to L Aarden.

At least 37 records · Page 2Linked to original sources
PubMed1993

Cytokines and intracellular signals involved in the regulation of B-CLL proliferation.

Cytokines play an important role in the regulation of both normal and malignant B cells. In this paper we give a brief overview of the major cytokines involved in the regulation of B-CLL proliferation. In vitro experiments have indicated that there is an antagonistic interaction between TNF-alpha as a growth-enhancing factor and IL-4, which inhibits the growth of B-CLL. We have extended these findings with recent experiments on the intracellular signals which might be involved in these processes. We show that increased levels of intracellular cAMP dose-dependently inhibit the TNF-alpha-induced proliferation of B-CLL. On the basis of these results, we propose a model for the signals involved in the regulation of B-CLL proliferation. The implications for possible new ways of treatment are discussed.

Apoptosis↗
PubMed1993

Differentiation of purified malignant B cells induced by PMA or by activated normal T cells.

We studied the in vitro differentiation (immunoglobulin production) of purified malignant B cells of 21 patients with different B-cell malignancies, including chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL), hairy cell leukemia (HCL) and non-Hodgkin lymphoma (NHL). Direct activation of purified malignant B cells with phorbol myristate acetate (PMA) resulted in the differentiation of most CLL cells, but not of the other types of B-cell malignancies. This differentiation required the presence of interleukin 4 (IL-4). In contrast, with the use of anti-CD2-stimulated normal T cells and IL-2, immunoglobulin M (IgM) could be detected in the supernatant of all but one of the purified malignant B-cell populations. However, by analysis of the light chains of the IgM produced, monoclonality could be demonstrated in only 13/21 cases: 8/11 CLL, 3/3 PLL, 0/3 HCL, and 2/4 NHL. In two patients additional proof that the malignant B cells were the source of the IgM production could be obtained in an idiotype-specific ELISA. Apart from IgM, also the production of IgG antibodies could be detected. However, only for 2/3 HCL patients, we could confirm a monoclonal IgG production. Since HCL is a malignancy of mature B cells, already carrying IgG on the membrane, this IgG production is not the result of a switch process. In all other cases where IgG production was polyclonal, we have no indications for the induction of Ig switch. The fact that the more mature B-cell malignancies were T-cell-dependent for their differentiation might be a reflection of the in-vivo situation. The efficient induction of malignant B-cell differentiation described in this paper allows investigation of the antigen specificity of these antibodies.

Antibodies, Anti-Idiotypic↗
PubMed1993

Effect of IL-4 and IL-6 on the proliferation and differentiation of B-chronic lymphocytic leukemia cells.

The proliferation and differentiation of purified malignant B cells from nine patients with chronic lymphocytic leukemia (B-CLL) were studied in vitro. We have demonstrated before that tumour necrosis factor alpha (TNF-alpha), in combination with low dose phorbol myristic acid (PMA) (0.1 ng/ml), can induce proliferation in these purified B-cell populations and that this TNF-alpha-induced proliferation is completely inhibited by the addition of interleukin 4 (IL-4). In this study we demonstrate that IL-6 is also able to inhibit this TNF-alpha-induced proliferation. Inhibition is maximal with 400 pg/ml of IL-6. With the use of neutralizing antibodies we show that the inhibition by IL-4 and IL-6 are independent processes. In contrast, investigation of differentiation as measured by immunoglobulin M (IgM) production, showed that in combination with PMA (1 ng/ml), IL-4 is the main cytokine to induce differentiation of these B-CLL cells. That we were indeed measuring differentiation of the malignant B cells could be demonstrated by the specific production of IgM/kappa or IgM/lambda. No induction of IgG or IgE production could be detected. In contrast to IL-4, in the majority of cases IL-6 does not play a role in the induction of differentiation of B-CLL cells. However, in two out of nine B-CLL patients we found that at low PMA concentrations (0.1 ng/ml), TNF-alpha can induce both proliferation and differentiation. In agreement with what was found for the proliferative response, this TNF-alpha-induced IgM production is inhibited both by IL-4 and IL-6. The possible therapeutic implications of our findings are briefly discussed.

Aged↗
PubMed1992

Interleukin-4 inhibits both paracrine and autocrine tumor necrosis factor-alpha-induced proliferation of B chronic lymphocytic leukemia cells.

The proliferative response of purified malignant B cells from 26 patients with chronic lymphocytic leukemia (CLL) was investigated in vitro. In the majority of these patients, a proliferative response could be induced by the combination of tumor necrosis factor (TNF)-alpha and PMA. The concentration of PMA was found to be critical and showed a sharp optimum. In most cases maximal proliferation was obtained with as little as 0.1 ng/mL PMA. In all cases tested, TNF-alpha-induced proliferation could be inhibited completely by the addition of low doses of interleukin-4 (IL-4). Maximal inhibition was already found with 400 pg/mL IL-4. Inhibition by IL-4 was not caused by a downmodulation of TNF receptors. Apart from TNF-alpha, IL-2 was also in synergy with PMA able to induce proliferation in B-CLL cells of some patients. This IL-2-induced proliferation could be inhibited both by IL-4 and by neutralizing anti-TNF-alpha antibodies. This shows that TNF-alpha also can act as an autocrine growth factor. These data indicate that TNF-alpha is an important growth factor for neoplastic B-CLL cells and that IL-4 provides a tool to interfere with this TNF-alpha response.

Adult↗
PubMed1992

Interleukin (IL)-4 production by human T cells: differential regulation of IL-4 vs. IL-2 production.

We have examined the regulation of interleukin (IL)-4 production by human peripheral blood T cells. Production of IL-4 was shown to be regulated differently from IL-2 and interferon(IFN)-gamma production. Stimulation of peripheral blood lymphocytes with anti-CD3, anti-CD2, anti-CD28, Phorbol 12-myristate 13-acetate (PMA) or IL-2 as a single stimulant did not induce IL-4 production. However, combinations of anti-CD2 with either anti-CD28 or IL-2 resulted in IL-4 production, peaking at days 3-4. Stimulation with anti-CD3 instead of anti-CD2 gave similar results, but was less potent. After days 3-4, IL-4 levels decreased, most likely due to consumption of IL-4. PMA profoundly affected cytokine production, it enhanced IL-2 production by at least tenfold, whereas, in the same cell population, IL-4 production was almost completely inhibited. This was observed at the protein as well as at the mRNA level. In contrast, agents that increase intracellular cAMP levels inhibited IL-2 production but left IL-4 production unaffected. IFN-gamma production behaved similar to IL-2 production but the effects were less outspoken.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1991

Monokine production by human T cells; IL-1 alpha production restricted to memory T cells.

The production of cytokines is a key event of inflammation. In this report we demonstrate that normal human T cells are capable to produce IL-1 alpha, IL-6, and TNF-alpha, cytokines formerly considered to be monokines. This production was optimal after stimulation with a combination of anti-CD2, PMA, and anti-CD28. All three cytokines were produced in a bioactive form. Both naive (CD4+CD45RA+) and memory (CD4+CD45RO+) subsets of T cells were shown to produce similar amounts of IL-6 and TNF-alpha. In contrast the production of IL-1 alpha was found to be completely restricted to the CD4+CD45RO+ subset. The finding that T cells are such potent producers of these important mediators of the inflammatory response might be a key observation in the appreciation of the role of T cells in chronic inflammation.

CD4 Antigens↗
PubMed1991

Sensitive ELISA for interleukin-6. Detection of IL-6 in biological fluids: synovial fluids and sera.

A monoclonal antibody and an affinity purified polyclonal antibody, both raised against recombinant human IL-6, have been employed in an ELISA procedure to quantitate human IL-6. Both antibodies were very potent in neutralizing the biological activity of recombinant as well as natural human IL-6. The monoclonal antibody was used as the capture antibody whilst the polyclonal antibody, in biotinylated form, was used as the detecting antibody in combination with a streptavidin horseradish peroxidase conjugate and a signal amplification system. The detection limit for natural as well as recombinant IL-6 was 1 pg/ml. A good correlation was found between the ELISA and the B9 biological assay when IL-6 was measured in crude culture supernatants, in synovial fluids of rheumatoid arthritis patients and in the sera of patients with diverse diseases. Immunoprecipitation of IL-6, produced by different cell types, such as monocytes, endothelial cells and smooth muscle cells or derived from biological fluids, such as the serum of a patient with septic shock or the synovial fluid of a rheumatoid arthritis patient, revealed in every case only molecules in the molecular weight range of 21,000-26,000.

Animals↗
PubMed1991

Interleukin-6 does not stimulate bone resorption in neonatal mouse calvariae.

Recombinant human interleukin-6 (IL-6) was assessed for its ability to stimulate bone resorption in prelabeled mouse calvariae in vitro. IL-6 had no effect on bone resorption at concentrations ranging from 300 to 10,000 U/ml (3-1000 pg/ml). Neither the presence of indomethacin nor prolonged incubation periods (96 h) affected this result. IL-6 did not affect resorption stimulated by human recombinant IL-1 alpha (rIL-1 alpha) but inhibited resorption stimulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. rIL-1 alpha, PTH, and 1,25-(OH)2D3 induced IL-6 release by calvariae. We conclude from these studies that IL-6 does not stimulate bone resorption in neonatal mouse calvariae. However, it may act as a locally produced inhibitor and therefore a paracrine regulator of bone resorption induced by osteotropic hormones. IL-6 could also function as a long-range stimulator of systemic reactions and acute-phase responses to local inflammatory and neoplastic lesions in bone.

Animals↗
PubMed1991

Cytokine-associated tissue injury and lethality in mice: a comparative study.

A comparative study was performed to examine the lethal effects of several cytokines injected into mice sensitized with actinomycin D (Act-D). Consistent with published data, human tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) (0.2-5 micrograms) caused the death of the animals within 8-12 hr after injection. Human interleukin-6 (IL-6) and interleukin-8 (IL-8) (0.6-6 micrograms) known to be induced by TNF-alpha did not show any lethal effects, indicating that TNF-alpha-associated lethality is not mediated by IL-6 or IL-8. Human tumor necrosis factor-beta (TNF-beta) (also called lymphotoxin), which shares structural and functional properties with TNF-alpha, was as potent as TNF-alpha in its lethal effects. Murine interferon-gamma (IFN-gamma) (0.04-5 micrograms) was also tested and showed no lethal effects in this model. In addition, a synthetic peptide corresponding to amino acid residues 163-171 of IL-1 beta, and which has been shown to lack the inflammatory effects of IL-1 beta, also caused no lethality among Act-D sensitized mice. The pretreatment of mice with IL-6, IL-8, or IFN-gamma had no protective effects on TNF-alpha or IL-1 beta-induced lethality in contrast to the protection observed by a pretreatment with TNF-alpha/IL-1 beta themselves or with endotoxin. Histopathologic data showed that severe tissue injury in vital organs is associated with the rapid lethality among sensitized mice.

Animals↗
PubMed1991

Differential induction of interleukin-6 production by monocytes, endothelial cells and smooth muscle cells.

Studying the production of IL-6 by monocytes, endothelial cells and smooth muscle cells we observed that cytokine inducers like IL-1, TNF alpha, LPS, SAC and PMA could be divided roughly into two categories. One, that consisted of LPS and SAC, which had a potent IL-6 inducing effect on monocytes and minor or no effect on endothelial- and smooth muscle cells. The other category, consisting of IL-1, TNF alpha and PMA, induced IL-6 production in endothelial- and smooth muscle cells and of which IL-1 also induced IL-6 in monocytes. Only IL-1 induced IL-6 production in monocytes as well as in endothelial cells and smooth muscle cells. Besides IL-6, also IL-1 and TNF alpha were produced by monocytes however with different kinetics. None of the stimuli had any inhibitory effect on IL-6 production with the exception of PMA. Whereas PMA induced IL-6 production in endothelial cells and it potentiated the induction of IL-6 by IL-1 in these cells, it inhibited LPS-stimulated IL-6 production in monocytes. In line with the effects of PMA, staurosporin induced IL-6 production in monocytes and it inhibited IL-1 driven IL-6 production by endothelial cells.

Antibodies, Monoclonal↗
PubMed1990

Interleukin-6 production by tumor necrosis factor and lipopolysaccharide-stimulated rat renal cells.

Interleukin-6 (IL-6) is produced by various cell types, including monocytes, fibroblasts, and endothelial cells. IL-6 has also been detected in the urine of normal and renal transplant patients. Thus, the possible production of this cytokine by glomeruli and mesangial cells was investigated. Rat glomeruli were obtained by serial sieving of cortical homogenates of blood-free kidneys. Mesangial cells were obtained from the glomeruli and cultured under standard methods in RPMI 1640 medium containing 15% fetal calf serum. Glomeruli or confluent monolayers cells were then incubated in RPMI 1640 for 18 hr, in the presence or not of tumor necrosis factor-alpha (TNF alpha), lipopolysaccharide (LPS), or platelet-activating factor (PAF). IL-6 activity was measured using the IL-6-dependent cell line subclone (B 9-9) and expressed with respect to a standard curve established with recombinant IL-6. Glomeruli generate IL-6 upon TNF alpha (100 ng/ml) and LPS (1 microgram/ml), 11,500 +/- 3000 and 22,000 +/- 7500 U/ml, respectively. Nonstimulated mesangial cells produced 50 +/- 5 U/ml (mean +/- SEM, n = 4) of IL-6. TNF alpha (1 ng/ml) and LPS (1 microgram/ml) induced the production of 800 +/- 90 and 40,000 +/- 5000 U/ml, respectively (n = 4). In contrast, PAF (0.1 nM-1 microM) did not increase IL-6 production from glomeruli or mesangial cells. These results demonstrate that renal cells spontaneously generate minimal amounts of IL-6 and that this production is significantly increased by TNF alpha or LPS. A synergy between LPS and TNF alpha was induced in glomerular cells with 10 ng/ml of TNF alpha and graded concentrations of LPS. Thus, the production of IL-6 by glomerular cells and its modulation by other cytokines or endotoxins may play a role in the local immunological processes leading to immune glomerular diseases.

Animals↗
PubMed1989

Comparison of the effects of recombinant interleukin 6 and recombinant interleukin 1 on nonspecific resistance to infection.

Interleukin 1 (IL 1) is a potent enhancer of nonspecific resistance to infection in mice. Since IL 1 also induces interleukin 6 (IL 6), we tested the hypothesis that IL 6 mediates the effect of IL 1 on nonspecific resistance. In a lethal Pseudomonas aeruginosa infection in granulocytopenic mice, in which 80 ng of recombinant human IL 1 alpha protects against death, IL 6 appeared to be much less effective. Dosages of 8 ng, 80 ng and 320 ng IL 6 did not differ from the control, whereas 800 ng had a marginal protective effect (0.05 less than p less than 0.1). IL 1 and IL 6 did not potentiate each other in animals treated with suboptimal dosages of both cytokines. Numbers of bacteria cultured from the blood, thigh muscle, liver, spleen, and kidney were similar in animals treated with 800 ng IL 6 and in control animals, arguing against activation of microbicidal mechanisms. The serum concentration profile of IL 6 after an i.p. injection of 80 ng IL 1 was similar to that after 80 ng IL 6 i.p. Only minute amounts of IL 1 were detected in serum after an i.p. injection of IL 6. Taken these data together, it appears that increased resistance to infection induced by IL 1 is not mediated by IL 6.

Animals↗
PubMed1989

Endotoxin, tumor necrosis factor-alpha and interleukin 1 induce interleukin 6 production in vivo.

The ability of Escherichia coli-derived lipopolysaccharide (LPS), recombinant (r) interleukin 1-beta (rIL-1 beta), and r murine tumor necrosis factor-alpha (rMuTNF-alpha) to induce interleukin 6 (IL-6) production in vivo was investigated. Peak serum IL-6 concentration was attained after 2 hr of LPS injection into mice. The coinjection of antiserum against rMuTNF-alpha with LPS resulted in a reduction of the induced serum IL-6 level, indicating the involvement of endogenous TNF-alpha in LPS induction of IL-6. Recombinant IL-1 beta and rMuTNF-alpha injected directly caused the production of substantial amounts of IL-6 within 30 min. The injection of a combination of rIL-1 beta and rTNF-alpha induced a significantly greater level of IL-6 than either agent alone. The greater level of serum IL-6 was associated with hypothermia and an increased lethality among mice injected with both cytokines. These data demonstrate the abilities of IL-1 beta and TNF-alpha to induce IL-6 production in vivo and indicate that LPS induction of IL-6 may be mediated, at least partially, through TNF-alpha action. The data describe a new in vivo biologic activity shared between IL-1 beta and TNF-alpha and suggest that IL-6 may be an important effector in the manifestation of TNF-alpha and IL-1 beta actions in vivo.

Animals↗
PubMed1989

Interleukin-6 induced at mucosal surfaces by gram-negative bacterial infection.

Interleukin-6 (IL-6) was produced in response to mucosal and systemic infection of mice with gram-negative bacteria. The IL-6 response was controlled by the lipopolysaccharide gene, Lps; in C3H/HeN mice (Lpsn/Lpsn), the urinary IL-6 levels increased within 30 min after challenge with Escherichia coli, but no response occurred in C3H/HeJ mice (Lpsd/Lpsd). In lipopolysaccharide-responder mice, the levels of local and systemic IL-6 were related to the degree of infection. The urinary response dominated after intravesical challenge, and the serum response dominated after intraperitoneal challenge. The results demonstrate that IL-6 is activated as part of lipopolysaccharide-induced mucosal and systemic responses to gram-negative bacterial infections.

Animals↗
PubMed1989

Studies on the monocyte dependence of T-cell proliferation induced by monoclonal antibodies directed against regions I and II of the CD2 antigen.

We produced three murine monoclonal antibodies (mAb) directed against the human T-cell differentiation antigen CD2 (formerly T11) and analysed their epitope specificity by E-rosette inhibition, cross-blocking and proliferation-induction experiments. When added together, two mAb (both IgG1 kappa) were able to induce proliferation in peripheral blood T cells. This proliferation was found to be strictly dependent on the presence of monocytes. The polymorphism of Fc receptors (FcR) expressed on human monocytes for murine IgG1 antibodies, which is readily demonstrable in anti-CD3-induced T-cell activation, was not found in the anti-CD2-driven system. Moreover, mAb directed against the 40,000 MW FcRII were unable to inhibit proliferation induced by the mitogenic anti-CD2 combination. Still, F(ab')2 fragments of the mitogenic anti-CD2 antibody combination could not initiate T-cell mitogenesis, despite their ability to induce a rise in the free intracellular [Ca2+]. The contributions of monocytes and of antibody Fc moieties to T-cell proliferation, induced by combinations of anti-CD2 mAb, will be discussed.

Antibodies, Monoclonal↗
PubMed1989

Paracrine rather than autocrine regulation of myeloma-cell growth and differentiation by interleukin-6.

To explore the mechanisms involved in the pathogenesis of human multiple myeloma (MM), we investigated the potential role of interleukin-6 (IL-6), a B-cell differentiation factor in humans, and a growth factor for rat/mouse heterohybridomas and murine plasmacytomas. Using a heterohybridoma assay, we found that two well-documented human myeloma cell lines, RPMI 8226 and U266, did not secrete IL-6 and did not express RNA messengers for IL-6. Neutralizing antibodies to IL-6 did not inhibit their proliferation, and recombinant IL-6 did not stimulate it. Taken together, these data show that IL-6 is not the autocrine growth factor of these human myeloma cell lines. A high production of IL-6 was found in the bone marrows of patients with fulminating MM, compared with patients with inactive or slightly active MM, or to healthy donors. This IL-6 production was assigned to adherent cells of the bone-marrow environment but not to myeloma cells. A spontaneous proliferation of myeloma cells freshly isolated from patients was observed in short-term cultures. Recombinant IL-6 was able to amplify it two- to threefold. The spontaneous proliferation of the myeloma cells was inhibited by anti-IL-6 antibodies and reinduced by recombinant IL-6. After 2 to 3 weeks of culture, the myeloma-cell proliferation progressively declined and no IL-6-dependent myeloma cell lines could be obtained despite repeated additions of fresh IL-6 and costimulation with other cytokines such as tumor necrosis factor (TNF)beta, or IL-1 beta. These data demonstrated a paracrine but not autocrine regulation of the growth and differentiation of myeloma cells by IL-6.

Aged↗