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Biomedical subjects

M Lotz

Publications and source records attributed to M Lotz.

At least 145 records · Page 8Linked to original sources
PubMed1988

B cell stimulating factor 2/interleukin 6 is a costimulant for human thymocytes and T lymphocytes.

Growth and differentiation of thymocytes and mature T lymphocytes is regulated by cellular interactions that are in part mediated by soluble factors. We identify IL-6, formerly called B cell stimulating factor (BSF-2). IFN-beta 2, or hybridoma-plasmacytoma growth factor (HPGF) as a novel T cell costimulant rIL-6 induced a six-to seven-fold increase in proliferation of human thymocytes stimulated with suboptimal doses of PHA. A similar effect with added IL-6 could be observed using peripheral blood T lymphocytes, but only if the cultures were first rigorously depleted of monocytes that release high levels of IL-6. Analysis of the mechanism of the IL-6 effect on thymocytes and T lymphocytes showed that IL-6 did not lead to an increase in IL-2-R expression. Concentrations of antibody to IL-2-R inhibiting IL-2 effects did not block the IL-6-induced proliferation, indicating that the IL-6 effect was relatively IL-2 independent. These results identify IL-6 as a novel costimulant of human thymocytes and mature T lymphocytes, and suggest that IL-6 is also an important regulatory of cellular immunity.

Cell Division↗
PubMed1987

Interferon-gamma is a major regulator of C1-inhibitor synthesis by human blood monocytes.

C1 inhibitor (C1INH) is the major control factor for the activation of the classical pathway of complement and for contact system activation. Hepatocytes and blood monocytes are known to synthesize this protease inhibitor. We studied the regulation of monocyte C1INH production by mediators that are generated during inflammatory responses. Purified blood monocytes spontaneously synthesized and secreted C1INH only after prolonged culture. In the presence of interferon (IFN)-gamma, C1INH was detectable within 24 hr and continued to be released at high levels throughout an 8-day culture period. Monocyte C1INH was newly synthesized and was functionally active as determined by forming stable complex with C1s. Other monocyte stimuli were either less potent (IFN-alpha, IFN-beta) or not capable of increasing C1INH release (lipopolysaccharide, interleukin 1, and tumor necrosis factor). The second component of complement, C2, was induced by IFN-gamma to a similar extent as C1INH. These findings demonstrate that IFN-gamma is a major regulator of monocyte C1INH production and may warrant consideration of IFN-gamma in the treatment of C1INH deficiency states.

Cells, Cultured↗
PubMed1987

Proliferating cell nuclear antigen (PCNA)/cyclin in activated human T lymphocytes.

Proliferating cell nuclear antigen (PCNA), also called cyclin, is an intranuclear polypeptide whose synthesis reaches its maximum during the S-phase of the cell cycle. PCNA is expressed in several kinds of proliferating cells, one of which is the mitogen-stimulated human peripheral blood lymphocyte. PCNA expression increases from the late G1 phase through the S-phase of the cell cycle. This study is focused on the regulation of PCNA expression during the G1 phase of human T lymphocytes and on the relationship between PCNA expression and the rate of T cell proliferation. Special use is made of human autoantibodies to PCNA and the development of flow cytometry to label this intranuclear polypeptide. Unstimulated purified human peripheral blood T cells were PCNA negative. T cells treated with monoclonal antibody (64.1) to the CD3 complex expressed receptors for IL 2 but did not express PCNA until exogenous IL 2 was added to the culture. PCNA expression as well as the entry of the cells into S-phase could be inhibited by IL 2 receptor antibodies. Transferrin receptors were expressed only in T cells that were stimulated with both 64.1 and exogenous IL 2. Transferrin receptors were detectable before the cells expressed PCNA. Thus, the onset of PCNA expression is a phase in cell proliferation that follows transferrin receptor expression but preceded DNA synthesis. Drugs like dexamethasone and cyclosporin, which affect the early part of G1, inhibited PCNA expression; whereas cytarabine (ara-C) and hydroxyurea, which affect the S-phase and prevent DNA synthesis, did not block PCNA expression. There was a close correlation between the number of PCNA-positive cells and the number of S-phase cells in unperturbed T cell cultures. The highest level of PCNA expression was seen in cells that were in the first cycle after stimulation. The results show that PCNA expression is regulated by a signal after IL 2 binding and that PCNA labeling is a precise indicator for human T cells that are committed to DNA synthesis. Comparing these results with previous observations on the expression of some other activation-associated antigens, we suggest that the onset of PCNA expression represents a discrete step in T cell activation.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1987

Substance P activation of rheumatoid synoviocytes: neural pathway in pathogenesis of arthritis.

Several clinical features are consistent with nervous system involvement in the pathogenesis of rheumatoid arthritis. The neuropeptide substance P is one possible mediator of this interaction, since it can be released into joint tissues from primary sensory nerve fibers. The potential effects of the peptide on rheumatoid synoviocytes were examined. The results show that substance P stimulates prostaglandin E2 and collagenase release from synoviocytes. Furthermore, synoviocyte proliferation was increased in the presence of the neuropeptide. Similar effects were observed with a truncated form of substance P. Synoviocytes were sensitive to very small doses of the neuropeptide (10(-9) M), and its effects were inhibited by a specific antagonist. Thus, the specific stimulation of synoviocytes by the neuropeptide substance P represents a pathway by which the nervous system might be directly involved in the pathogenesis of rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1987

Effects of recombinant human interferons on rheumatoid arthritis B lymphocytes activated by Epstein-Barr virus.

We evaluated the effects of all 3 classes of recombinant human interferon (IFN) on Epstein-Barr virus (EBV) infection of purified B lymphocytes from patients with rheumatoid arthritis (RA). After EBV infection, RA B cells secreted more IgM and significantly more IgM rheumatoid factor (RF) than normals. Spontaneous (no EBV) proliferation, IgM, and IgM RF were also higher in RA. All 3 types of IFN inhibited dose dependently EBV induced B cell activation. In RA, however, higher doses of each class of IFN were necessary to obtain 50% inhibition. IFN gamma was most potent in normals and RA. Four IgM RF production IFN gamma was significantly more potent than IFN alpha and IFN beta in reducing the spontaneous activation of RA B cells, and a similar trend was seen in B cell proliferation. These findings are discussed in the context of ongoing clinical trials with IFN gamma in RA.

Adult↗
PubMed1986

Release of lymphokines after Epstein Barr virus infection in vitro. I. Sources of and kinetics of production of interferons and interleukins in normal humans.

Infection of human lymphocytes with Epstein Barr virus (EBV) activates the release of lymphokines. Previous experiments have emphasized the ability of interferon-gamma (IFN-gamma) to prevent EBV-induced B cell transformation. However, the factors that regulate IFN-gamma synthesis and release during in vitro EBV infection are controversial. In the present investigation we have systematically evaluated the kinetics of production, cellular origins, and accessory cell requirements for IFN-alpha and IFN-gamma and for IL 1 and IL 2, after EBV infection. Our data indicate that IFN-alpha is released entirely by natural killer (NK) cells and B cells, in the absence of accessory cells, independently of the other lymphokines and within 24 hr of infection. In contradistinction, IFN-gamma secretion is exclusively of T cell origin, is absolutely dependent on the prior elaboration of IL 1 and IL 2, and is maximal 8 days after EBV infection. IL 2 secretion by T cells peaks on day 5 and requires the earlier release of IL 1. Both NK cells and monocytes are a source of IL 1. Secretion of IL 2 and IFN-gamma occurs in the presence of either one of these cell types but not in the absence of both. Antibody against IL 1 blocks EBV-induced IL 2 and IFN-gamma generation, and antibody against IL 2 decreases production of IFN-gamma. Thus, the production of IFN-gamma, the lymphokine that prevents EBV-induced B cell transformation, is the final outcome of a cascade of lymphokine-mediated events that involve interactions between virus-infected B lymphocytes that serve as antigen-presenting cells, NK cells and monocytes as sources of IL 1, and T lymphoblasts. Dysfunctions of any or all of these cell types would be expected to impair the regulation of EBV transformation.

Adult↗
PubMed1986

Release of lymphokines after infection with Epstein Barr virus in vitro. II. A monocyte-dependent inhibitor of interleukin 1 downregulates the production of interleukin 2 and interferon-gamma in rheumatoid arthritis.

Epstein Barr virus (EBV)-infection of normal peripheral blood mononuclear cells (PBMC) in vitro induces IFN-alpha secretion from B cell and natural killer (NK) cell populations, and IFN-gamma secretion from T cells. IFN-gamma depends on prior elaboration of IL 2 and IL 1 that originates from monocytes and NK cells. PBMC from rheumatoid arthritis (RA) patients released moderately elevated levels of IFN-alpha (236 +/- 62 U/ml vs 168 +/- 34 in normals). In contrast, IFN-gamma was significantly lower in RA (88 +/- 34 U/ml vs 209 +/- 32) with an associated deficit in IL 2. A monocyte-dependent factor was shown to be responsible for this deficit, since monocyte depletion of RA cultures normalized the levels of IL 2 and IFN-gamma. Significantly lower levels of IL 1 activity were present in the supernatants of RA PBMC cultures as compared with normal cultures, and this was shown to be associated with presence of a nondialyzable IL 1 inhibitor. This inhibitor was capable of preventing the IL 1-dependent synthesis of IL 2 and IFN-gamma by normal PBMC. Exogenous IL 1 or IL 2 restored the deficient IFN-gamma secretion in RA PBMC. Thus, the deficient ability of RA lymphocytes to control EBV infection may be secondary to impairment of a monocyte-T cell interaction at the level of IL 1.

Adult↗
PubMed1986

Basis for defective responses of rheumatoid arthritis synovial fluid lymphocytes to anti-CD3 (T3) antibodies.

Synovial fluid mononuclear cells (SFMC) from patients with active rheumatoid arthritis characteristically respond poorly to mitogens. In this study, mitogenic antibodies reactive with the CD3(T3) antigen on human T lymphocytes were used to analyze the basis for the deficiency. OKT3-induced proliferation and release of interleukin 1 (IL-1) and interleukin 2 (IL-2) from SFMC were depressed in all patients. Purified IL-1 or recombinant IL-2 restored proliferative responses in SFMC and increased IL-2 receptor density. Exogenous IL-1 also enhanced IL-2 release. Fractionation of SFMC supernatants on phosphocellulose columns revealed the presence of IL-1 and a potent IL-1 inhibitor. The monocyte-derived IL-1 inhibitor blocked IL-1-dependent responses of normal peripheral blood lymphocytes to OKT3, but had no effect on IL-2-dependent events. These results suggest that IL-1 inhibitor(s) in SFMC impair(s) OKT3-induced mitogenesis by interfering with the effects of IL-1 on T lymphocytes. The net result is deficient IL-2 secretion, IL-2 receptor expression, and impaired cellular proliferation. This novel inhibitory circuit provides a rational explanation for the diminished function of synovial fluid T lymphocytes in rheumatoid arthritis patients.

Adult↗
PubMed1986

Lymphoblastoid B cell lines produce an interleukin-1-like activity that can be serologically distinct from macrophage interleukin-1.

Antigen presentation by macrophages is accompanied by the production of interleukin-1 (IL-1) for successful T cell triggering. We have described EBV infected B cell lines that served as antigen presenting cells (APC) and now report the ability of these cells and their supernates, as well as EBV negative B cell lines, to support IL-2 production by a T cell line JM in the presence of the monoclonal antibody that recognizes the CD3 complex. Both EBV-transformed B cell lines and EBV-negative lines, and their supernates, exhibited IL-1-like activity in two different IL-1 dependent assays. These IL-1-like molecules were released constitutively from five of six EBV positive lines and three of five non-infected B cell lines. The activity from both, one virally infected and one non-infected B cell line, eluted from Sephadex G-75 in two peaks at 15-18K and 30-35K and could not be neutralized by antibody specific for macrophage IL-1. Supernates having IL-1-like molecules also contained a higher molecular weight inhibitor of proliferation. These data indicate that: both EBV-positive and EBV-negative B cell lines are capable of elaborating the IL-1-like activity; and the IL-1-like activity from these cells can be serologically distinct from macrophage IL-1. This suggests the presence of a family of molecules with IL-1 activity that derive from different cell types.

Animals↗
PubMed1985

Regulation of Epstein-Barr virus infection by recombinant interferons. Selected sensitivity to interferon-gamma.

Interferons (IFN) are antiviral proteins that may be important in mediating cellular defenses against Epstein-Barr virus (EBV) infection. However, the means by which IFN-alpha, -beta and -gamma modify EBV infectivity are not clear. We have evaluated the effects of purified recombinant preparations of all three classes of IFN on EBV-induced B lymphocyte proliferation and Ig secretion. When added early after EBV infection, all three recombinant IFN reduced B cell outgrowth and Ig secretion. IFN-gamma exerted a 7-10-fold more potent antiviral effect than IFN-alpha or -beta. All three types of IFN act directly on B cells. Monocytes and natural killer cells are not necessary for the anti-EBV activity. Of the three recombinant IFN, only IFN-gamma reduced EBV-induced proliferation and Ig secretion when added 3-4 days after virus infection; IFN-alpha/beta were only effective up to 24 h. B lymphoblastoid lines already transformed by EBV are insensitive to the anti-proliferative actions of all three types of IFN. On the basis of these findings, we propose three phases of regulation during EBV infection. In the early phase, EBV-infected cells can be regulated by all IFN. Subsequently, there is an intermediate period where only IFN-gamma is capable of directly affecting EBV-induced B cell responses. In the third phase, B lymphocytes become insensitive to direct actions of all IFN and are now subject to regulation only by cytotoxic cells.

B-Lymphocytes↗
PubMed1985

The role of the T3 molecular complex on human T lymphocyte-mediated cytotoxicity.

The above overview of the experimental data clearly indicates that the T3 molecular complex is intimately involved in T cell activation. The precise role of the T3 complex in the activation process, however, is not clearly understood. The surface association of the T3 complex with the antigen receptor, along with the ability of antibodies to these molecules to render T cells receptive to IL2, reveal a possible mechanism by which specific antigen initiates T cell activation and growth. However, it would be difficult to reconcile this specific effect of anti-T3 antibodies with their effect on CTL function. Since the T3 complex is not a specific marker of any particular effector T cell population, but it is found on all T lymphocytes, we favor the hypothesis that the complex is involved in a more fundamental step of T cell activation, and we believe that triggering of the 'lethal hit', expression of IL2 receptors, and secretion of IL2 are mere manifestations of this basic process. The natural ligand of the antigen receptor is obviously the specific antigen. However, the natural ligand of the T3 complex is unknown. Possibly, its natural ligand is the antigen receptor itself after it has interacted with antigen. A simple scenario, then of the early events of T cell activation would include antigen recognition and binding, followed by an interaction between the antigen receptor and the T3 complex which then activates or allows expression of specific pathways depending on the particular effector population involved. Thus, the inhibition of CTL function by anti-T3 antibodies could be explained by interference with the antigen receptor-T3 complex interaction following target cell recognition. This interaction may be the event that signals the initiation of the 'lethal hit' process.

Antibodies, Monoclonal↗
PubMed1985

Activation of resting T lymphocytes by anti-CD3 (T3) antibodies in the absence of monocytes.

The antigen receptor molecules on human T lymphocytes are noncovalently associated on the cell surface with the CD3 (T3) molecular complex. Perturbation of this complex with anti-CD3 monoclonal antibodies induces T cell activation. Previous studies have demonstrated that this process requires the participation of monocytes. In the present report, we demonstrate that purified, resting (G0 phase) T cells incubated with monoclonal anti-CD3 antibodies proliferate in response to purified interleukin 2 (IL 2), in a lymphokine dose-dependent fashion. Anti-CD3 antibody or IL 2 alone did not trigger cell division. The effect was specific for anti-CD3 antibodies because monoclonal antibodies reactive with other surface molecules (OKT4, OKT8, L368) were inactive. Furthermore, the same phenomenon was observed when anti-CD3 antibody Leu-4 (IgG1) was incubated with cells of individuals whose monocytes cannot process antibodies of the IgG1 subclass (Leu-4 nonresponders). In addition, both F(ab')2 and Fab fragments of anti-CD3 antibody OKT3 were also capable of rendering T cells receptive to the IL 2 growth signal. These data indicate that neither monocytes nor CD3 receptor cross-linking are required absolutely for resting T cell activation, provided that IL 2 is supplied exogenously. T lymphocytes treated with anti-CD3 antibodies proliferated in response to both purified mitogen-induced and recombinant IL 2. Antibodies to the IL 2 receptor (anti-Tac) inhibited the proliferation. Thus, the most likely mechanism for anti-CD3 antibody-mediated triggering is induction of IL 2 receptors.

Antibodies, Monoclonal↗
PubMed1984

Lymphocyte mitogenesis induced by monoclonal antibodies to the T3 complex. Differential modulation by human IgG.

Murine monoclonal antibodies OKT3 (IgG2), 64.1 (IgG2), and Leu 4 (IgG1) react with a common membrane antigen on human T cells and induce potent mitogenesis at concentrations of 1 ng/ml, 10 ng/ml, and 100 ng/ml, respectively. Human serum inhibits the mitogenic effect of antibodies OKT3 and 64.1, but not that of Leu 4. The inhibitor in serum has been identified as immunoglobulin G (IgG) as evidenced by the ability of anti-human IgG-Sepharose affinity columns to retain the inhibitory activity. Various immunoglobulin classes and subclasses obtained from human myelomas differ in their ability to inhibit the OKT3-induced activation. The best inhibition is obtained with the IgG subclasses IgG1 and IgG3, followed by IgG2; IgG4, IgM, and IgA have little if any effect. None of the IgG subclasses inhibit the Leu 4-induced mitogenesis. Indomethacin as well as supernatants containing interleukin 2 (IL-2) can reverse the inhibitory effects of IgG. Prostaglandins (PGE1 and PGE2) inhibit both the OKT3- and Leu 4-induced mitogenesis, thus lacking the selectivity seen with IgG. Since stimulation by the monoclonal antibodies requires the participation of monocytes, an interpretation consistent with the present data is that IgG stimulates monocytes via its Fc portion to release prostaglandins and/or other suppressor factors via an indomethacin-sensitive pathway. The inability of IgG to inhibit Leu 4-induced mitogenesis may therefore relate to an inability of the monocyte subpopulation, which mediates the Leu 4 response, to secrete suppressor factors. These data suggest a potential value of the mitogenic monoclonal antibodies as probes in studying monocyte heterogeneity and T-cell-monocyte interactions.

Antibodies, Monoclonal↗