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Biomedical subjects

M R Shalaby

Publications and source records attributed to M R Shalaby.

At least 37 records · Page 2Linked to original sources
PubMed1988

Pharmacokinetics of recombinant murine interferon-gamma and human interferon-alpha A/D(Bgl) administered in concert and their influence on natural killer cell function in mice.

The pharmacokinetics of recombinant murine interferon-gamma (rMuIFN-gamma) administered alone and in combination with recombinant hybrid human interferon-alpha (rHuIFN-alpha A/D-[Bgl]) were studied following intravenous (i.v.) and intramuscular (i.m.) injections into mice. The concomitant influence of these IFNs on splenic natural killer (NK) cell function was also examined. The coinjection of both IFNs did not affect the pharmacokinetics of either after i.v. administration. However, simultaneous injection of both IFNs i.m. does result in statistically significant changes in the serum concentrations of rHuIFN-alpha A/D(Bgl). The clinical benefits of the increased bioavailability of rHuIFN-alpha A/D(Bgl) are not apparent since NK cell enhancement after both IFNs were injected together was the same as that obtained after injection of rHuIFN-alpha A/D(Bgl) alone. NK cell enhancement after both IFNs were injected together was the same as that obtained after injection of rHuIFN-alpha A/D(Bgl) alone. Correspondingly, the coinjection of both IFNs did not affect the pharmacokinetics of either.

Animals↗
PubMed1987

Inhibition of cytokine production by cyclosporin A and transforming growth factor beta.

We investigated the ability of cyclosporin A (CsA) and transforming growth factor beta (TGF-beta) to modulate the production of TNF-alpha and TNF-beta and IFN-gamma by unseparated, nonadherent, and adherent PBMC. Treatment of unseparated PBMC with CsA resulted in a significant dose-dependent inhibition of all three cytokines ranging from greater than 90% inhibition for IFN-gamma and TNF-beta, to approximately 70% for TNF-alpha. Pretreatment of unseparated or nonadherent PBMC with TGF-beta inhibited the production of IFN-gamma by 60-70%. However, the inhibition of TNF-alpha and TNF-beta production by these cells was only minimally affected, and at 0.1-1 ng/ml TGF-beta could enhance TNF-alpha production by unseparated PBMC. In contrast, pretreatment of adherent PBMC with TGF-beta inhibited the production of TNF-alpha by approximately 60%. TGF-beta also inhibited both TNF-alpha production and tumor cell cytotoxicity mediated by murine peritoneal-derived macrophages. These observations indicate that the biological effects of CsA and TGF-beta on immune functions are of a wider range than previously reported.

Animals↗
PubMed1987

Characterization of the antitumor activities of human tumor necrosis factor-alpha and the comparison with other cytokines: induction of tumor-specific immunity.

We have investigated the in vitro and in vivo antitumor activities of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) against Meth A sarcoma. Meth A sarcoma cells were found to a) be relatively insensitive in vitro to rHuTNF-alpha, and b) express low numbers of TNF-alpha receptors. Intraperitoneally implanted Meth A sarcoma was insensitive to the antitumor effects of rHuTNF-alpha. In contrast, rHuTNF-alpha was highly efficacious against subcutaneously implanted Meth A sarcoma. Biodistribution studies with 125I- or 3H-labeled rHuTNF-alpha demonstrated that, after intravenous administration, the majority of the labeled rHuTNF-alpha localized in the kidney, lungs, and liver. Only low levels of radiolabel were found in subcutaneous Meth A implants. These results support the in vitro data on the low number of TNF-alpha receptors on Meth A sarcoma cells. The ability of rHuTNF-alpha to induce regression of established (7 days) subcutaneous Meth A implants, positively correlated with the degree of both macroscopic and microscopic tumor necrosis. In addition, recombinant human tumor necrosis factor-beta (lymphotoxin) and recombinant murine tumor necrosis factor-alpha induced similar levels of necrosis. Other lymphokines with known antitumor activities, recombinant human interferon-gamma, murine interferon-gamma, and human interleukin 1 alpha, failed to induce detectable necrosis of Meth A sarcoma. Mice which had rejected subcutaneous Meth A sarcoma implants after rHuTNF-alpha treatment and which were later challenged subcutaneously with Meth A sarcoma or other noncross-reacting chemically induced sarcomas were found to be specifically immune to Meth A sarcoma. In addition, low levels of cytotoxic antibodies reactive to Meth A sarcoma were detected in the sera of 21 of 30 Meth A immune mice. Histological evaluation of the hemorrhagic tumor necrosis induced by rHuTNF-alpha suggests that the primary lesion is vascular, possibly directly on the endothelial cells. The mechanisms involved in the generation of specific cell-mediated antitumor immunity in this model are at present unknown.

Animals↗
PubMed1987

Possible relationships between in vivo antitumour activity and toxicity of tumour necrosis factor-alpha.

The discoveries of a tumour necrosis-inducing substance in sera of experimental mice and of cytotoxic factor(s) in cultures of stimulated lymphoid cells triggered intense research efforts which have culminated in the production of two distinct but related recombinant materials, human tumour necrosis factors TNF-alpha (cachectin) and TNF-beta (lymphotoxin). The necrosis of tumours by TNF is but one feature of high doses of these immune system hormones that possess numerous biological activities. Apart from their direct cytotoxic/cytostatic activities against tumours in vitro and in vivo, the in vivo antitumour activities of TNF-alpha or TNF-beta may involve the following biological activities: the induction of interleukin 1 production; activation of polymorphonuclear neutrophil functions; modulation of endothelial cell functions; and augmentation of specific immune functions. Many of these activities are associated with an irreversible acute inflammation which appears to be the immediate lethal effect of TNF on transplantable tumours in mice. This inflammation leads to thrombosis, disruption of the tumour's blood supply and, finally, tumour death. Inflammatory effects of high doses of TNF are also seen in the rodent gastrointestinal tract but here the inflammation seems to be reversible.

Animals↗
PubMed1987

Receptor binding and activation of polymorphonuclear neutrophils by tumor necrosis factor-alpha.

The interaction of highly purified recombinant human tumor necrosis factor-alpha (rTNF-alpha) with human polymorphonuclear neutrophils (PMNs) was investigated. Binding of 125I-rTNF-alpha to PMN reached maximum levels in 30 min at 37 degrees C and in 2 h at 4 degrees C. Scatchard analysis of competitive binding data indicated approximately 6000 receptor sites per cell and a Kd of 1.37 nM. Binding data at 37 degrees C indicated a rapid internalization of rTNF-alpha. Following this receptor-mediated interaction, recombinant TNF-alpha was found to inhibit the migration of PMNs under agarose and to enhance PMN production of superoxide anion (O-2) in a dose-dependent manner. Furthermore, rTNF-alpha-activated PMNs caused a marked disruption of human umbilical-vein-derived endothelial cell monolayers and caused inhibition of their proliferative activities. These data substantiate the role of TNF-alpha as an activator of PMN functions and indicate that PMN/TNF-alpha/endothelial cell interactions may play a major role in inflammatory reactions.

Binding, Competitive↗
PubMed1987

The effects of human immunodeficiency virus recombinant envelope glycoprotein on immune cell functions in vitro.

The effect of human immunodeficiency virus (HIV) recombinant envelope glycoprotein 120 (rgp 120) on the functions of peripheral blood mononuclear cells (PBMC) in vitro was investigated. The results demonstrate that rgp 120 used at concentrations less than 1 microgram/ml has no significant effects on PBMC function in vitro. However, the addition of 1-20 micrograms/ml of rgp 120 significantly inhibits the tetanus toxoid-induced PBMC proliferative response in a dose-related manner as determined by [3H]thymidine incorporation. The data also show that rgp 120 (5 micrograms/ml) causes up to 70% reduction in the number of immunoglobulin G-secreting cells in pokeweed mitogen-stimulated PBMC cultures. Further, rgp 120 can selectively interact with the CD4a epitope of the CD4 helper cell membrane receptor. These results indicate that microgram per milliliter levels of rgp 120 can depress certain immune functions in vitro. The significance of these findings to the pathogenesis of immunodeficiency in HIV infection remains to be determined.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

Natural killer-sensitive targets stimulate production of TNF-alpha but not TNF-beta (lymphotoxin) by highly purified human peripheral blood large granular lymphocytes.

Highly purified populations of large granular lymphocytes (LGL) have been shown to mediate natural killer (NK) cell activity. The mechanism of target cell killing by NK cells is as yet undefined; however, it has been postulated that such killing may involve soluble cytotoxic factors produced and secreted by NK cells. The data presented show that NK-sensitive, but not NK-resistant, tumor cell lines induce highly purified populations of human LGL to produce factors with cytotoxic and/or cytostatic activities. We have identified one of these factors as tumor necrosis factor-alpha (TNF-alpha), and have shown that production of this factor is enhanced by recombinant human interferon-gamma (rHuIFN-gamma). We have also examined the role of TNF-alpha in the cytotoxic function of NK cells. The data show that although highly purified LGL populations produce low levels of TNF-alpha, the cytotoxic/cytostatic activity of this lymphokine on tumor target cells does not correlate with the cytotoxic activity of highly purified populations of LGL on tumor target cells. Furthermore, NK cell-mediated cytotoxicity is not reliably inhibited by antibodies directed against various epitopes of recombinant human TNF-alpha and/or recombinant TNF-beta (lymphotoxin) or rHuIFN-gamma. These data show that although TNF-alpha is produced by highly purified NK-containing LGL cell populations, this factor does not appear to be responsible for NK cell cytotoxicity against classical NK target cells such as Molt-4 or K562. We suggest that NK function can be attributed to a combination of factors rather than to a single factor alone, and that at least two major phenomena are involved in LGL function: the rapid cytotoxic events which lead to the cell lysis measured in classical in vitro NK assays such as against K562; and the release of factors such as TNF-alpha with cytotoxic/cytostatic activities which would inhibit the growth of invading tumor cells in vivo.

Animals↗
PubMed1985

In vivo antiviral activity of recombinant murine gamma interferon.

Recombinant murine gamma interferon (gamma-IFN) was tested for its antiviral activity in vivo. IFN preparations purified to greater than 95% purity were administered to CD-1 mice infected with lethal doses of encephalomyocarditis (EMC) virus. An initial treatment with rMuIFN-gamma administered 4 h prior to infection with virus, followed by daily treatment for 3 consecutive days significantly protected mice against EMC virus as evidenced by animal survival after 3-4 weeks post-viral infection. Variations in the antiviral effect relative to dose levels and routes of administration were also studied.

Animals↗
PubMed1985

In vivo augmentation of natural killer activity by combined treatment with recombinant gamma interferon and interleukin-2.

The in vivo regulation of natural killer (NK) cell function by recombinant murine gamma interferon (rMuIFN-gamma) and recombinant human interleukin-2 (rHuIL-2) was investigated. Peritoneal exudate-derived natural killer (PE-NK) cells of mice treated with rMuIFN-gamma or rHuIL-2 exhibited significantly enhanced cytolytic activities against YAC-1 target cells. Compared with animals receiving treatment with either rMuIFN-gamma or rHuIL-2 alone, the sequential treatment of mice with both agents resulted in a significantly greater enhancement of PE-NK cell function, especially when rMuIFN-gamma was administered 24 h before treatment with rHuIL-2. The cytolytic activities were significantly diminished after pretreatment of effector cells with anti-Qa-5 antiserum and complement but not with anti-Lyt-3.2 antiserum. These data constitute the first evidence demonstrating the association between IFN-gamma and IL-2 in the regulation of NK cell function in vivo, reinforce the potential benefit of combined treatment with biological response modifiers, and show that the schedule of administration may be a critical requirement for optimal benefits of combined lymphokine treatment in vivo.

Animals↗
PubMed1985

Activation of human polymorphonuclear neutrophil functions by interferon-gamma and tumor necrosis factors.

Recombinant human interferon-gamma (rHuIFN-gamma) and natural human tumor necrosis factor beta (nHuTNF-beta) (previously called lymphotoxin), purified to homogeneity, were used to assess their effects on certain functions of human polymorphonuclear neutrophils (PMN) in vitro. The treatment of PMN with 100 U of either rHuIFN-gamma or nHuTNF-beta for 20 min significantly increased their ability to phagocytize 1.5-microns latex beads as detected by flow cytometry. Preparations of recombinant human TNF-beta (rHuTNF-beta) showed activities similar to those of its natural counterpart in activating phagocytosis. In addition, a significant enhancement in PMN-mediated antibody-dependent cellular cytotoxicity was observed after treatment for 2 hr with IFN gamma and both TNF-alpha and TNF-beta. The enhancement by treatment with a combination of rHuIFN-gamma and nHuTNF-beta exceeded the enhancement caused by either agent alone. We also show that although lipopolysaccharide (LPS) is a potent stimulator of PMN function, polymyxin B can block LPS-induced but not lymphokine-induced activation. These data demonstrate new activities for both TNF-alpha and TNF-beta in augmenting the phagocytic and cytotoxic activities of PMN.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1985

Interferon gamma: more than a MAF.

The precise immunoregulatory activities of particular lymphokines have been difficult to define due to the presence of contaminating molecules in the purified natural preparations under study. Thus, the application of recombinant DNA technologies to lymphokine research has been instrumental in elucidating the biologic properties of many of these factors. In particular, with the availability of recombinant gamma interferon (rIFN-gamma) a variety of immuno-regulatory functions, including natural killer activation, enhancement of lymphokine production, macrophage activation, and cell surface Ia expression, have been clearly shown to be mediated by this lymphokine. Recently we have compared the properties of macrophage activating factor (MAF) to those of natural and rIFN-gamma. This article reviews our evidence suggesting that IFN-gamma is a major MAF. In addition, we present evidence for another activity of IFN-gamma, namely, its ability to regulate the growth of certain interleukin 2 (IL-2)-dependent cytotoxic T cell lines.

Animals↗
PubMed1984

Effects of bacteria-produced human alpha, beta, and gamma interferons on in vitro immune functions.

The effects of bacteria-produced human interferons (HuIFN) alpha, beta, and gamma on in vitro immune functions of human peripheral blood mononuclear cells (PBMC) were studied. Proliferative response to phytohemagglutinin was significantly inhibited by the addition of HuIFN-alpha 2 or HuIFN-beta at 10, 100, or 1000 U/ml. In contrast, HuIFN-gamma showed suppressive activities only when added at 1000 U/ml. HuIFN-alpha 2 or HuIFN-beta caused significant inhibition of human mixed-lymphocyte reaction (MLR) as measured by [3H]thymidine incorporation. Similar inhibition was caused by HuIFN-gamma when it was added only at very low concentrations (1 U/ml); 10, 100, or 1000 U/ml resulted in no or only a modest increase in MLR. All three interferons exhibited dose-related effects on PWM-induced immunoglobulin synthesis in cultures of PBMC. These data demonstrate that purified interferons produced by recombinant DNA technology can significantly alter in vitro immune functions and that HuIFN-gamma has properties which are different from those of HuIFN-alpha 2 or HuIFN-beta.

Antibody-Producing Cells↗
PubMed1984

Augmentation of human natural cell-mediated cytotoxicity by recombinant human interleukin 2.

Human peripheral blood mononuclear cells (PBMC) demonstrated increased natural cell-mediated cytotoxicity (NCMC) activity after only 5 min of exposure to purified recombinant human IL 2 or interferon (IFN)-gamma. The mechanism of NCMC augmentation by treatment with IL 2 is not entirely dependent on IFN-gamma production because: a) IL 2 was found to augment NCMC activity at levels which did not induce detectable IFN-gamma; b) IL 2 required only 5 min of exposure to PBMC to augment NCMC activity, whereas 3 hr of contact were required to demonstrate detectable IFN-gamma levels; c) the levels of NCMC enhancement by treatment with IL 2 exceeded the amount of NCMC enhancement that could be due to IFN alone; d) anti-recombinant IFN-gamma, which totally eliminated the augmentation of NCMC enhancement by IFN-gamma, only partially reduced the augmentation of NCMC activity by IL 2; and e) combination treatment of PBMC with IL 2 and IFN-gamma resulted in a synergistic enhancement of NCMC. The results strongly support the conclusion that augmentation of NCMC by IL 2 and IFN-gamma involve overlapping mechanisms.

Cytotoxicity, Immunologic↗
PubMed1983

Bacteria-derived human leukocyte interferons alter in vitro humoral and cellular immune responses.

Cultures of gradient-purified human peripheral blood mononuclear cells (PBMC) have been employed to examine the effects of three bacteria-derived human leukocyte interferon subtypes on certain aspects of in vitro immune responses. The addition of highly purified IFN-alpha 1, -alpha 2, -alpha 2/alpha 1 to PMBC cultures stimulated with phytohemagglutinin (PHA) or pokeweed mitogen resulted in a significant suppression of the mitogenic response. This suppression required the presence of interferon in the cultures because pretreatment of cells and removal of interferon had no effect on their response to PHA. The presence of these interferons at 200 U/ml also caused a substantial reduction of human mixed-lymphocyte reactions (MLR) as measured by [3H]thymidine incorporation by responder cells. Interestingly, pretreatment of stimulator cells was sufficient for this reduction to occur whereas pretreatment of responder cells had no effect on their ability to respond to allogenic stimulation. In contrast to these suppressive effects, the three interferons enhanced human in vitro primary immune response to sheep red blood cells (SRBC). These data demonstrate that both purified interferon subtypes and genetic hybrids of human interferons produced by recombinant DNA technology have effects on in vitro immune responses.

Antibody Formation↗
PubMed1983

The mechanism of appearance of specific antibody-forming cells in lungs of inbred mice after intratracheal immunization with sheep erythrocytes.

Immunization, ablation, and adoptive transfer studies were performed in inbred mice to define in vivo the cellular mechanisms for the appearance of specific antibody-forming cells (AFC) in pulmonary parenchyma. Mice were immunized locally or systemically with sheep erythrocytes (SRBC), and the concentrations of IgM- and IgG-producing AFC were measured in lung and extrapulmonary lymphoid tissues with a hemolytic-plaque assay. Splenectomized mice and recipients of adoptively transferred, sensitized lymphocytes were examined. We found that primary intratracheal (IT) immunization regularly failed to induce the appearance of AFC in lungs, whereas IT boosting of primed animals consistently succeeded. Immunization experiments showed that mice could be primed by any of a variety of local or systemic routes, but that the IT route of boosting was an absolute requirement for the induction of pulmonary AFC in primed mice. Recruitment of AFC into lungs by IT boosting of systemically primed and boosted animals was antigen-specific. Splenectomy performed prior to priming reduced, but did not ablate, the pulmonary AFC-response to IT boosting. Adoptive transfer of sensitized lymphocytes to naive recipient mice substituted for antigen-priming, which is required for induction of pulmonary AFC by IT challenge. Results of adoptive transfer studies demonstrate that IT challenge with specific antigen recruits systemically administered sensitized lymphocytes into the lung. We conclude that local primary immunization of mice results in the generation of AFC in extrapulmonary lymphoid tissues and that the major mechanism for the appearance of AFC in lungs is through recruitment of sensitized cells from systemic sources by intrapulmonary boosting with specific antigen.

Animals↗
PubMed1980

An indirect assay for canine leukocyte migration inhibitory factor (LIF): demonstration of its species specificity.

An indirect assay in agarose-gel was developed to measure secretion of leukocyte migration inhibitory factor (LIF) by canine lymphocytes. Supernatants from cultures of mitogen- or alloantigen-stimulated canine peripheral blood lymphocytes were assayed for LIF activity using purified granulocytes as indicator cells. Canine LIF activity could be detected provided either autologous or allogeneic canine granulocytes were used as indicator cells. In contrast, canine LIF uniformly failed to inhibit the migration of human granulocytes. Likewise, human LIF inhibited the migration of human but not canine granulocytes in this assay. The data indicated that this species specificity could be due to differences in the structures of LIF receptors on canine and human granulocytes.

Acetylglucosamine↗
PubMed1980

Canine surface active material and pulmonary lymphocyte function. Studies with mixed-lymphocyte culture.

Canine bronchoalveolar cells, obtained by lavage, were enriched for lymphocytes by adsorption to plastic or by filtration over nylon wool and tested for their ability to function in the mixed lymphocyte culture (MLC) reaction. Pulmonary lymphocytes were markedly hyporesponsive to stimulation with allogeneic cells in vitro: their responses rarely exceeded 10% of those of blood lymphocytes obtained simultaneously from the same donor. However, pulmonary lymphocytes did function as stimulating cells, inducing allogeneic blood lymphocytes to proliferate in MLC. The failure of pulmonary lymphocytes to respond in MLC, coupled with their ability to stimulate clearly, distinguishes these cells from circulating blood lymphocytes. The effect of canine surface active material (SAM), a lipoprotein unique to the lung, on the function of blood lymphocytes in MLC was studied. A transient exposure to SAM in vitro profoundly suppressed blood lymphocyte responses to allogenic stimulation, but had only a minor effect on their function as stimulator cells in MLC. Thus, exposure to SAM in vitro converts normal blood lymphocytes into cells whose function mimics that of pulmonary lymphocytes. These results suggest that exposure of pulmonary lymphocytes to SAM in vivo may contribute to their abnormal immune reactivity in vitro.

Animals↗