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Biomedical subjects

A Meager

Publications and source records attributed to A Meager.

At least 109 records · Page 6Linked to original sources
PubMed1989

Spontaneous and interleukin 2 induced secretion of tumour necrosis factor and gamma interferon following autologous marrow transplantation or chemotherapy.

Culture of lymphocytes from allograft recipients or from normal donors with Interleukin 2 (IL2) induces high levels of gamma-interferon (gamma IFN) and tumour necrosis factor (TNF) secretion. We now show that production of these two cytokines can also be increased after autologous bone marrow transplantation (BMT) and induced following chemotherapy for haematological malignancy. These effects occur even though the regenerating IL2 responsive lymphocytes in this context have previously been extensively exposed to cytotoxic agents. IL2 induced secretion of gamma-IFN and TNF is higher in autograft recipients than in patients treated by chemotherapy alone. This effect may be related to differences in the phenotypic profile between recovering lymphocytes in the two groups and to an increased degree of prior in vivo lymphocyte activation in the autologous bone marrow transplant recipients. In both groups of patients, IL2 acts on CD3+ T cells and on CD16+ NK cells so that depletion of either subset incompletely abrogates IL2 dependent gamma-IFN secretion. As both TNF and gamma-IFN possess anti-leukaemic and anti-infective activity, enhancement of their secretion by IL2 infusion after autologous bone marrow transplant and induction after chemotherapy may be of therapeutic benefit.

Adolescent↗
PubMed1989

Human T cell responses to dengue virus antigens. Proliferative responses and interferon gamma production.

The severe complications of dengue virus infections, hemorrhagic manifestations and shock, are more commonly observed during secondary dengue virus infections than during primary infections. It has been speculated that these complications are mediated by cross-reactive host-immune responses. We have begun to analyze human T cell responses to dengue antigens in vitro to explain the possible role of T lymphocytes in the pathogenesis of these complications. Dengue antigens induce proliferative responses of PBMC from dengue antibody-positive donors, but do not induce specific proliferative responses of PBMC from dengue antibody-negative donors. IFN gamma is detected in the culture fluids of dengue-immune PBMC stimulated with dengue antigens. The cells that proliferate in the dengue antigen-stimulated bulk cultures have CD3+, CD4+, CD8-, CD16-, and CD20- phenotypes. Dengue-specific T cell lines were established using limiting dilution techniques. They have CD3+, CD4+, and CD8- phenotypes, and produce IFN gamma in response to dengue antigens. Culture fluids from dengue-immune PBMC stimulated with dengue antigens, which contain IFN gamma, augment dengue virus infection of human monocytes by dengue virus-antibody complexes. These results indicate that PBMC from dengue-immune donors contain CD4+ T cells that proliferate and produce IFN gamma after stimulation with dengue antigens, and suggest that the IFN gamma that is produced by these stimulated dengue-specific T cells may contribute to the pathogenesis of dengue hemorrhagic fever and dengue shock syndrome by increasing the number of dengue virus-infected monocytes in the presence of cross-reactive anti-dengue antibodies.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Lipoarabinomannan from Mycobacterium tuberculosis induces the production of tumour necrosis factor from human and murine macrophages.

We show here that purified lipoarabinomannan (LAM) from Mycobacterium tuberculosis can cause the release of tumour necrosis factor (TNF) in vitro from human blood monocytes and activated mouse peritoneal macrophages, and the production of TNF in vivo in mice pretreated with Propionibacterium acnes, with a potency comparable to that of lipopolysaccharide (LPS) from Gram negative bacteria. Like LPS, LAM binds to polymyxin B. We confirmed that its activity was distinct from any contaminating LPS and was associated with the antigenic activity by affinity chromatography, using a monoclonal antibody specific for LAM. Treatment with dilute alkali greatly diminished the TNF-inducing activity, suggesting that omicron-acyl groups may be involved. When LAM was fractionated by electrophoresis on SDS-Page and blotted on nitrocellulose, most TNF-inducing capacity coincided with the bulk of the LAM, as estimated by molecular weight and antigenic activity. This modification of the Western blotting technique may be generally useful for the study of macrophage-triggering molecules. The ability of LAM to cause the release of TNF may be responsible for some of the characteristics of tuberculosis, such as fever, weight loss, raised acute phase reactants and necrosis that can be mediated by this cytokine.

Animals↗
PubMed1989

In vivo induction of gamma interferon and tumor necrosis factor by interleukin-2 infusion following intensive chemotherapy or autologous marrow transplantation.

Interleukin-2 (IL-2) therapy may improve immune reconstitution and reduce the risk of leukemic relapse in the setting of minimal residual disease by augmenting cytotoxic effector mechanisms directed at residual malignant cells. In addition, IL-2 in vitro promotes the release of cytokines including gamma-interferon (gamma-IFN) and tumor necrosis factor (TNF), which also possess antileukemic activity and can enhance granulocyte function. To determine if IL-2 infusion induces release of gamma-IFN and TNF in vivo in sufficient quantity to mediate these effects, we have measured serum levels of these cytokines and secretion by lymphocytes obtained from patients receiving this cytokine in a phase 1 trial. Serum gamma-IFN was undetectable pre-IL-2 and increased to 1.5 to 17 U/mL during IL-2 infusion (P less than .05). Culture of patient lymphocytes for 48 hours produced 1.2 U gamma-IFN/2 x 10(6) cells/mL pre-IL-2 rising to 50 U/2 x 10(6) cells/mL when the lymphocytes were obtained during therapy (P less than .05). Lymphocyte subset analysis showed that both CD3+ and CD16+ cells secreted gamma-IFN in response to IL-2. TNF secretion by lymphocytes also rose during IL-2 infusion from a mean of 5 U/mL to 14.4 U/mL (P less than .01) although no rise was seen in serum levels. The material secreted by IL-2-stimulated lymphocytes is bioactive as addition of supernatants from lymphocytes obtained during IL-2 therapy to cultures of myeloid blasts significantly inhibited clonogenic growth. IL-2-induced secretion of these cytokines mediated this inhibition as it could be partially blocked by either anti-gamma-IFN or anti-TNF antibodies. Preincubation of granulocytes with the same supernatants produced enhanced oxidative metabolism, measured by chemiluminescence in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP). This effect also could be partially abrogated by anti-gamma-IFN and anti-TNF antibodies. Therefore, secondary cytokine secretion may boost granulocyte function and contribute to the antileukemic effects of IL-2 infusion in patients following bone marrow transplantation or chemotherapy.

Adolescent↗
PubMed1989

Release of cytokines during generation of lymphokine-activated killer (LAK) cells by IL-2.

Supernatants of IL-2-activated mononuclear cells (MNC) that displayed an optimal lymphokine-activated killer (LAK) cell activity at 48-72 hr in culture were found to contain increased levels of tumour necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha) and interferon-gamma (IFN-gamma) when compared with supernatants from mononuclear cells cultured in the absence of IL-2. The concentration of TNF alpha and IL-1 alpha produced by MNC at 24 hr was either increased or maintained by extending the cultures to 96 hr. In contrast, TNF beta was only detected at very low levels after 72-96 hr culture, irrespective of whether IL-2 was present or absent. Optimal concentrations of IL-2 needed to induce maximum release of TNF alpha, IL-1 alpha and IFN-gamma by MNC varied among different individuals. Enriched populations of lymphocytes secreted higher levels of all measured cytokines upon activation with IL-2 in contrast to untreated cells. Supernatants from purified monocyte preparations contained high concentrations of TNF alpha and IL-1 alpha regardless of the presence of IL-2 in the cell cultures. This work suggests that in addition to the generation of LAK cell activity, by promoting the release of other cytokines with potential anti-tumoricidal activity, IL-2 may be amplifying cell-mediated cytotoxicity, which is associated with protection against neoplastic disease.

Biological Factors↗
PubMed1988

Clonal analysis of functionally distinct human CD4+ T cell subsets.

A large number of CD4+ T cell clones, obtained from peripheral blood T lymphocytes by direct limiting dilution, allowed us to address the question whether functional heterogeneity exists within the human CD4+ T cell subset. Cytotoxic capacity of cloned T cells was analyzed with the use of anti-CD3 antibodies and target cells bearing FcR for murine IgG. 6 of 12 CD4+ clones obtained were able to lyse Daudi or P815 cells in the presence of anti-CD3 antibodies. The remaining six CD4+ T cell clones tested did not display anti-CD3-mediated cytotoxic activity and did not acquire this cytotoxic capacity during a culture period of 20 wk. In the absence of anti-CD3 mAb, no lytic activity against Daudi, P815, and K562 target cells was observed under normal culture conditions. Phenotypic analysis of these two distinct types of CD4+ T cells did not reveal differences with regard to reactivity with CDw29 (4B4) and CD45R (2H4) mAbs that have been described to recognize antigens associated with helper suppressor/inducer (respectively) CD4+ cells. The CD4+ clones without anti-CD3-mediated cytotoxic activities (Th2) consistently showed a high expression level of CD28 antigens, whereas the cytotoxic clones (Th1) expressed low amounts of CD28. Th1 CD4+ clones did produce IL-2, IFN-gamma, and TNF-alpha/beta, whereas the Th2 T cell clones produced minimal amounts of IL-2 and only low levels of INF-gamma and TNF-alpha/beta in response to anti-CD3 mAbs and PMA. Although not all CD4+ clones did release IL-4, there was no correlation with cytotoxic activity. Moreover, as compared with the Th1 CD4+ clones, Th2 CD4+ T cell clones proliferated moderately in response to immobilized anti-CD3 mAbs. However, proliferation reached the level of the cytotoxic clones when anti-CD28 mABs were present during culture. Both CD4+ subsets provided help for B cell differentiation upon stimulation with anti-CD3 mAbs. Our data suggest that the human CD4+ subset, in analogy to the murine system, comprises two functionally distinct T cell subpopulations, both of which are able to exert helper activity for polyclonal B cell differentiation, but which differ in cytotoxic capacity, lymphokine production, and requirements for proliferation. A function for these two types of T cells in the immune response is discussed.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Enhanced tumour necrosis factor and interleukin-1 in fulminant hepatic failure.

Sepsis and endotoxaemia are common in fulminant hepatic failure (FHF) and may contribute to multisystem disease in such patients. Tumour necrosis factor (TNF) is a probable mediator of endotoxic shock and infusion of this monokine into animals causes multi-organ failure that shares features with FHF. In patients with FHF, TNF production was increased and correlated closely with activity of interleukin-1, another cytokine that is released by monocytes/macrophages in response to infection and endotoxin and is produced in increased quantities in FHF. Interleukin-2 activity was impaired in FHF and correlated negatively with TNF production.

Adolescent↗
PubMed1988

Production of B cell stimulatory factor-2 and interferon gamma in the central nervous system during viral meningitis and encephalitis. Evaluation in a murine model infection and in patients.

Synthesis of B cell-stimulating factor-2 (BSF-2) and IFN-gamma was shown in cerebrospinal fluids (CSF) collected from mice with experimental viral meningitis. In the CSF, the level of BSF-2 started to increase 24 h after intracerebral infection with lymphocytic choriomeningitis virus (LCMV) with rapid increase after day 4. IFN-gamma was not detected in the CSF before day 5 or 6 after infection, but increased sharply thereafter. In athymic nude mice, LCMV infection did not result in meningitis, and both BSF-2 and IFN-gamma levels were only slightly and transiently elevated. These findings suggest that activated mature T cells are required for development of disease and production of both BSF-2 and IFN-gamma. As observed in mice, BSF-2 was also detected in 16 out of 19 CSF samples collected from patients with acute viral infections of the central nervous system (CNS). Intrathecal production of BSF-2 and IFN-gamma may be instrumental in local production of antiviral antibodies by B lymphocytes/plasma cells invading the CNS during viral CNS disease.

Adult↗
PubMed1988

Tumour necrosis factor as an autocrine tumour growth factor for chronic B-cell malignancies.

Recombinant tumour necrosis factor (TNF) promotes survival and induces proliferation in the tumour cells from two malignancies of B lymphocytes--hairy-cell leukaemia and B-chronic lymphocytic leukaemia. Culture with TNF also induces TNF mRNA and protein, so the cytokine may act as an autocrine tumour growth factor. These growth promoting effects are antagonised by alpha but not by gamma interferon.

B-Lymphocytes↗
PubMed1988

Localization of alpha-interferon in the human feto-placental unit.

The distribution of alpha-interferon in human placental tissue was investigated by immunocytochemical study of paraffin wax-embedded tissue sections using a sheep alpha-interferon antiserum. Fifty-eight placentas of gestational ages from 8 to 40 weeks were examined. alpha-Interferon was present in the syncytiotrophoblast of the chorionic villi of all placentas and was also in macrophages in 28 cases. The appearances suggest production of interferon in human placental trophoblast and, in view of its diverse biological effects, support the concept of a role for alpha-interferon in the complex series of events required for successful gestation.

Chorionic Villi↗
PubMed1988

Cytokines in synovial fluid: II. The presence of tumour necrosis factor and interferon.

Cytokine-specific monoclonal antibodies were used in enzyme-linked immunoadsorbant assays (ELISA) to examine a variety of synovial fluids for the presence of cytokines which might be expected to play some part in the pathology of arthritis. Low, but significant, levels of tumour necrosis factor alpha (TNF-alpha) were present in the majority of synovial fluids obtained from rheumatoid arthritis patients with a sero-positive history. Low levels of interferon (IFN)-alpha and IFN-gamma were also detected, but only IFN-alpha was significantly increased in the sero-positive group. Tumour necrosis factor beta (TNF-beta) was present only in trace amounts. These results suggest that the presence of cytokines, such as TNF-alpha and IFN-alpha in synovial fluid may be associated with tissue changes observed in rheumatoid joint disease and thus contribute to the pathology of the arthritis, but support evidence for the minimal role likely to be played by IFN-gamma in the joint pathology of rheumatoid arthritis.

Arthritis↗
PubMed1988

Biological standardization of cytokines.

Cytokines are a heterogenous group of biologically active proteinaceous molecules which regulate cell growth, differentiation and function. They are secreted, soluble (non-antibody) mediators which are active in very small quantities and thus may be considered to be a subset of hormones. Many cytokines, especially those affecting the immune system, are being evaluated in the clinic, mainly in the area of cancer therapy. Cytokines constitute a group of proteins which cannot be completely characterized by chemical and physical features alone. Since they are highly biologically active and generally have wide-ranging pharmacological effects, they must necessarily be characterized from a biological standpoint. For convenience, the biological properties of cytokines are assessed in responsive in vitro cell systems. The development of specific biological assays to measure cytokine activities has rapidly progressed in the last decade and has led to attempts to standardize these activities. Standardization of interferons in terms of antiviral activity, for example, has been largely successful in establishing a common international unitage for interferon activity. The latter was dependent on the development and establishment of WHO international interferon reference preparations or standards. Standardization of other cytokines including interleukin-1, interleukin-2 and tumour necrosis factor is currently underway and interim reference preparations have been made available. It is likely that there will be a growing requirement for biological standardization of colony stimulating factors and other growth and differentiation factors.

Biological Factors↗
PubMed1988

Assay of pyrogenic contamination in pharmaceuticals by cytokine release from monocytes.

In 1984 it was reported that a batch of human recombinant growth hormone which had passed the rabbit pyrogen test and a Limulus amoebocyte lysate (LAL) test was pyrogenic in man (1). Further, it was shown that the growth hormone caused human monocytes to release leukocyte pyrogen which evoked fevers in rabbits (1). Leukocyte pyrogen is believed to comprise of a mixture of (at least) 2 lymphokines with potent pyrogenic and inflammatory activities, interleukin-1 (IL-1) and Tumour Necrosis Factor (TNF), which are synthesized and released by activated peripheral blood monocytes. The development at NIBSC of sensitive and specific bioassays and immunoassays of IL-1 (2) and TNF (3) have permitted a new type of pyrogen test based on the in vitro release by human monocytes of the lymphokines IL-1 and TNF. Studies are underway to evaluate the suitability of monocytic cell lines, rather than human monocytes, since these require a time-consuming and labour intensive preparation. Investigations are in progress to evaluate the suitability of the above "monocyte test" for pyrogen to replace or complement the rabbit pyrogen test which is routinely applied to biological medicines. The new method has already proved useful in detecting pyrogenic contamination of a large volume parenteral medicinal product which passed the rabbit pyrogen test but caused adverse reactions in patients.

Cells, Cultured↗
PubMed1987

Immunoreactive alpha-interferon in insulin-secreting beta cells in type 1 diabetes mellitus.

Of 37 pancreases removed at necropsy from patients with type 1 diabetes 34 had residual beta cells. In 33 of the 34 the beta cells were positive for immunoreactive alpha-interferon, and this finding in islets was related to hyperexpression of class I major histocompatibility complex (MHC) antigens. Of islets showing class I hyperexpression 93% contained alpha-interferon compared with 0.4% of those showing no hyperexpression. Among 80 control pancreases significant numbers of beta cells containing alpha-interferon were present only in 4 cases of acute infantile viral pancreatitis, known to be caused by Coxsackie-B viral infection in 3 cases. Chronic viral infection of beta cells may underlie the pathogenesis of some cases of type 1 diabetes.

Acute Disease↗
PubMed1987

A two-site sandwich immunoradiometric assay of human lymphotoxin with monoclonal antibodies and its applications.

Three monoclonal antibodies (MoAbs L49-15, L81-11 and L238-14) were raised against recombinant human lymphotoxin (rLT) derived from E. coli containing the cDNA sequence specifying LT. MoAb L81-11 strongly neutralised the cytotoxicity of LT derived either from E. coli or the RPMI 1788 lymphoblastoid cell line, whilst the other two MoAbs were only weakly neutralising in this respect. L81-11 and L238-14 MoAbs bound to different antigenic determinants on the rLT molecule, but neither bound to other lymphokines such as the structurally related tumour necrosis factor (TNF). As such, these MoAbs were ideal reagents for immunoassay of LT and a very sensitive, highly specific immunoradiometric assay (IRMA) was developed. This assay was rapid to perform and was capable of detecting as little as 10 pg/ml of LT. Application of the LT IRMA in combination with previously developed human gamma-interferon (IFN-gamma) and human TNF-specific IRMA (Crane et al., 1985; Meager et al., 1987) permitted independent estimations of these three substances to be carried out in parallel. By these means, it was found that RPMI 1788 produced both LT and TNF, but not IFN-gamma. Extensive analyses on cytokine (monokine and lymphokine) preparations derived from a variety of activated lymphocytes are also reported. Co-production of LT, TNF and IFN-gamma was a common finding, even occurring in alloantigen-specific T helper cell clones.

Antibodies, Monoclonal↗
PubMed1987

Preparation and characterization of monoclonal antibodies directed against antigenic determinants of recombinant human tumour necrosis factor (rTNF).

A large number of monoclonal antibodies (McAb) binding to antigenic determinants of human tumour necrosis factor (TNF) were prepared from two fusions of mouse myeloma NSO cells with spleen cells from Balb/c mice immunized with highly purified recombinant (r)TNF. Several of these McAbs were highly neutralizing with respect to the biological activity (cytotoxicity) of TNF manifested in L-929 C1.10 cells. Antibody competition experiments suggested the presence of at least two antigenic determinants on the rTNF molecule through which binding of McAb effects neutralization of biological activity. Some of these McAbs were shown to be suitable for the development of immunoassays to quantify rTNF.

Animals↗
PubMed1987

Production of interferon and tumour necrosis factor by cloned human natural cytotoxic lymphocytes and T cells.

Cell lines and clones, derived from natural killer (NK) cell-enriched (B73.1+) peripheral blood lymphocytes (PBL) from several human donors, that expressed distinct surface phenotypes and were cytolytically active against K562 target cells were tested for their capacity to produce interferon (IFN) and tumour necrosis factor (TNF), IFN and TNF were measured firstly in biological assays and secondly in specific immunoassays for alpha-IFN, gamma-IFN and tumour necrosis factor (TNF alpha). It was found that the majority of NK-derived lines and clones were highly cytotoxic towards K562, but generally produced relatively low or undetectable levels of gamma-IFN and TNF alpha following stimulation with phytohaemagglutinin. No alpha-IFN was detected in supernatants from these cells. In comparison, cell lines and clones, derived from T lymphocyte (B73.1-) enriched PBL from the same donors were poorly cytotoxic towards K562, but generally produced higher levels of gamma-IFN and TNF than NK-derived cells. Thus, neither gamma-IFN nor TNF production were shown to correlate well with the capacity of NK-derived or T cell clones to effect cytotoxic action towards K562 in vitro. These results suggest that the co-production of gamma-IFN and TNF is not indicative of cytotoxic potential.

Antigens, Surface↗