Thymus-like activities of sulphur derivatives on T-cell differentiation

Effect of levamisole on pokeweed mitogen stimulation of immunoglobulin production in vitro

The effects of levamisole (LMS) on immunoglobulin (Ig) production were studied in vitro using peripheral blood lymphocytes from normal subjects stimulated with pokeweed mitogen (PWM). Cells were cultured for 9 days with varying concentrations of LMS and PWM, and immunoglobulin secretion in the supernatants was quantified by solid phase radioimmunoassay. The results showed that 1) the effect of LMS in vitro depends upon the degree of lymphocyte stimulation by PWM. When PWM stimulation is optimal, typical pharmacologic concentrations of LMS (0.5 micro/ml) decrease both IgM and IgG production by 50%. However, at lower suboptimal doses of PWM, LMS, at similar concentrations, enhances immunoglobulin production by 24% (p less than 0.01). Unstimulated lymphocytes are not affected by LMS. 2) The target cell upon which LMS acts is present among a T subpopulation that lacks the Fc receptor for aggregated rabbit IgG (T gamma -negative). We suggest that the diverse effects of LMS on autoimmune disease in vivo may depend upon both the size and degree of activation of the T gamma -negative lymphocyte pool.

Serum Sulfhydryl Concentrations in Patients with Malignant Lymphoma

The total concentration of protein suifhydryl (SH) groups was determined in the sera of 15 patients with untreated malignant lymphoma (4 patients with Hodgkin's disease and 11 with non-Hodgkin's malignant lymphoma) using 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB). Serum SH total concentration in all patients was markedly depressed and significantly lower than that observed in the sera of healty controls matched for sex and age.

Levamisole in patients with recurrent herpes infection

The effect of the immunomodulating drug levamisole was tested in 33 patients with frequently recurring attacks of herpes labialis or herpes genitalis. All patients had suffered monthly recurrent attacks for at least six months, but were otherwise healthy. Patients were randomly allocated to receive levamisole tablets, 2.5 mg/kg orally, on two consecutive days each week for 26 weeks, or placebo tablets taken for a similar time. The tablets were reversed for a second consecutive six-month period. Seven of 21 patients (33%) with recurrent herpes genitalis infection showed complete response and 10 (47%) showed a partial response while receiving levamisole. Three of 21 patients (14%) showed a partial response on placebo. Six of 12 patients (50%) with herpes labialis showed complete or partial responses, with three partial responses on placebo. Frequent minor drug side effects were seen, and therapy was ceased in one patient. No episodes of leucopenia or agranulocytosis were encountered. Levamisole produces a significantly better reduction in frequency, duration and severity of herpes attacks than placebo, particularly after the initial eight weeks of administration.

The general immunopharmacology of levamisole

The need for treatments to correct an immunological defect, or to restore an impaired immune response asociated with disease or ageing, has led to the development of nonspecific immunoactive agents. Levamisole, a synthetic low molecular weight compound, is the first member of a new class of drugs which can increase the functions of cellular immunity in normal, healthy laboratory animals. The properties of levamisole have contributed to improved understanding of the molecular events which mediate or trigger immune responses. Levamisole can act either as an immunostimulant agent or an immunosuppressive agent. These apparently paradoxical effects depend upon the dose administered, the timing of its administration, the experimental assay used to measure effects, and the host genetic background. Levamisole's potential for opposite effects explains certain apparent inconsistencies observed in experimental or clinical assays. The drug's actions are modulated by the interaction between the T-cell recruiting efficacy of the sulphur moiety and the cholinergic effects of the imidazole ring. The clinical implications resulting from the immunopharmacological properties of levamisole are obvious: one should avoid its use in diseases without known association with an immune defect, and always attempt to correlate clinical data with modifications of immune parameters, since the therapeutic usefulness of correctly administered levamisole parallels improvement in tests of cellular immunity. Immunomodulators act by modifying the functions of the host cells involved in defences against invaders, and the effectiveness of an immunotherapeutic drug is dependent upon characteristics of the individual host. Thus, therapy with such drugs must be individualised; the appropriate agent and dosage should be chosen according to the immune capabilities of individual patients.

Suppression of pokeweed mitogen-induced differentiation of human B cells by in vitro levamisole-treated T lymphocytes

The generation of immunoglobulin-producing cells from human peripheral blood lymphocytes in pokeweed mitogen-simulated cultures was significantly suppressed by levamisole. Greatest suppression was observed when cells were incubated with levamisole at a concentration of 10(-6) M for 20 min or more prior to culture. Such suppression occurred when untreated as well as levamisole-treated B cells were co-cultured only with levamisole-treated T cells. Adding of levamisole-treated T cells to a combination of untreated autologous B and T cells resulted in the suppression of B cell differentiation. The results suggest that levamisole treatment of lymphocytes exerts suppression on pokeweed mitogen-induced B cell differentiation through its effect on T cell regulatory properties.

Effect of short-term levamisole therapy on delayed hypersensitivity

A randomized trial of short-term Levamisole treatment was undertaken in a cancer population unresponsive to dinitrochlorobenzene (DNCB) to determine whether this agent increased delayed hypersensitivity. Of 100 patients entered, 50 received Levamisole (150 mg daily x 3) during DNCB challenge. The other 50 patients were challenged but not given the drug. The conversion rate to DNCB+ was 20% (10/50) for those treated and 12% (6/50) for controls. The difference is not significant. When all 100 patients were considered there was a statistically significant inverse relationship between extent of disease and the incidence of conversion to a DNCB reactive state. Levamisole as given does not appear to have a major influence on delayed cutaneous hypersensitivity.

Induction of differentiation of human null cells into T lymphocytes under the influence of serum of mice treated with sodium diethyldithiocarbamate

Mouse serum collected 24 hr after administration of sodium diethyldithiocarbamate was shown to convert a subset of null cells, not bearing the human T lymphocyte differentiating antigen (HTLA cells) into HTLA+ cells in man. In addition to inducing surface characteristics of T lymphocytes, the serum of treated mice increased functional activities of human peripheral blood lymphocytes, including the response to Con A and the suppressor activity in vitro.

Levamisole inhibition of microsomal lipid peroxidation as related to its sulfhydryl metabolite dl-2-oxo-3-(2-mercaptoethyl)-5-phenylimadazolidine

Levamisole was previously shown to protect rat liver microsomes from lipid peroxidation induced by ADP-Fe and either NADPH, ascorbate, or X irradiation. The present experiments provide information about the mechanism of protection. Incubation of levamisole with a microsomal system containing ADP-Fe and NADPH resulted in protection of sulfhydryl groups, whereas reaction of levamisole with ascorbate (nonenzymatic system) indicated generation of a sulfhydryl metabolite. Production of a sulfhydryl metabolite of levamisole, dl-2-oxo-3-(2-mercaptoethyl)-5-phenylimidazolidine (OMPI), in either the enzymatic or nonenzymatic system was demonstrated by gas chromatography-mass spectrometry. While levamisole acts as an antioxidant at concentrations of 1.0 and 2.0 mM, OMPI had an enigmatic effect on microsomal lipid peroxidation induced enzymatically or nonenzymatically. OMPI exhibited a biphasic effect: at concentrations below 25 microM a prooxidant effect was observed, and at concentrations exceeding 50 microM an antioxidant effect was observed. The data suggest that the inhibition of microsomal lipid peroxidation by levamisole is due to the generation of a sulfhydryl metabolite and that the active intermediate is probably OMPI.

Serum sulfhydryl levels in rheumatoid patients treated with cyclophosphamide

Six months' cyclophosphamide treatment significantly increased the sulfhydryl (SH) serum levels in all 12 rheumatoid arthritis (RA) patients studied and significantly decreased the PIP joints' technetium index (Tc-index), the erythrocyte sedimentation rate (ESR), and the joint count.

Differentiation and regulation of lymphocyte populations: evidence for immunopotentiator-induced T cell recruitment

Isoprinosine, the p-acetaminobenzoic acid salt of inosine dimethylaminoisopropanol (1:3 molar ratio) and sodium diethyldithiocarbamate are two immumopotentiators which share an ability to induce in vivo acquisition of a specific T-cell marker by undifferentiated precursor lymphoid cells of healthy nu/nu mice, without affecting the B-cell lineage. Serum from treated nu/nu mice tested in dual assays, contains a selective inducer of prothymocytes.

Genetic and epigenetic control of levamisole-induced immunostimulation

Antibody responses to a T-cell dependent antigen, sheep red blood cells, were evaluated in mice of various inbred strains, treated or untreated, with levamisole. These responses appear to be under polygenic control, not associated with the H-2 complex, and modified by a Y-linked component and epigenetic factors revealed by aging. Strain, sex, age and the dose of levamisole all in influenced in an interrelated manner the activity of levamisole. Effects varied from inhibited to unchanged or increased antibody-forming cell numbers, without a direct relationship between the genetic regulation of levamisole effectiveness and a genotypic capacity to respond to the antigenic signal. Therefore, a complex relationship between host, antigen and immunopotentiator appears to be responsible for modifying the production of suppressor or helper influences. The present findings may serve as a warning against the uncritical use of levamisole.

Immunopotentiation and anabolism induced by sodium diethyldithiocarbamate

Sodium diethyldithiocarbamate, DTC, enhances over a large range of doses macrophage listericidal capacity and T cell activities in terms of increased IgG-antibody forming spleen cells and delayed hypersensitivity levels. Such immunopotentiation is not associated with splenomegalia or increase in lymphocyte counts. Immunopotentiation requires a preexisting link between carbon disulfide and diethylamine, since both moieties were inactive if administered alone or on separate body sites. DTC demonstrates also an anabolic effect on mice emanciated by administering a B. melitensis cell-wall fraction. The role of DTC on hormonal production is discussed in relation to hormone-mediated action on T cell induction.

T-cell lymphoma induction by radiation leukemia virus in athymic nude mice

We report the development of extrathymic lymphoblastic lymphomas in RadLV-inoculated congenitally athymic nude mice. Thus, a leukemogenic virus which appears to require the presence of a thymus for its replication in normothymic mice can infect and transform target cells in the absence of this organ in the athymic host. The cells of one of these lymphomas have been established in vitro as a permanent cell line, BALB/Nu1. This cell line as well as a lymphoma induced in NIH/Swiss nude mice exhibit several T-cell markers, including terminal deoxynucleotidyl transferase activity, Thy-1.2, and Ly-2.2, but not Ly-1.2 nor TL. Ig determinants were not detected. The characteristics of the tumor cells support the view that cells with T-cell markers may normally exist in nude mice and undergo neoplastic transformation and clonal expansion after infection with a leukemogenic virus. The alternative possibility that virus-induced differentiation of prothymocytes may lead to the expression of Thy-1.2 and Ly-2.2 antigens is also considered. BALB/Nu1 cells release large numbers of type C viral particles. The virus, designated radiation leukemia virus (RadLV)/Nu1, has RTase activity and the protein profile characteristic of murine leukemia virus (MuLV). In radioimmunoassays, it cross-reacts completely with RadLV/VL3, a virus obtained from RadLV-induced C57BL/Ka thymic lymphoma cells in culture, and slightly with a xenotropic virus (BALB:virus-2) and with AKR MuLV. On inoculation into C57BL/Ka mice it has thymotropic and leukemogenic activity. In vitro it is B-tropic, poorly fibrotropic, and has limited xenotropic activity. Thus, RadLV/Nu1 appears to be biologically and serologically similar or identical to its parent virus, RadLV.

DL-2-Oxo-3-(2-mercaptoethyl)-5-phenylimidazolidine. A sulfhydryl metabolite of levamisole that interacts with microtubules

DL-2-Oxo-3-(2-mercaptoethyl)-5-phenylimidazolidine (OMPI) a sulfhydryl metabolite of levamisole, unlike the parent compound, is shown to interfere with the morphological and functional integrity of microtubules in cultured cells at high concentrations (1.6-10(-4) M). Lower concentrations do not affect the cell morphology, viability or growth rate in any appreciable way. Both levamisole and OMPI, at low concentrations (10(-5)-10(-6) m), markedly enhance the antimicrotubular effect of mercaptoethanol. High concentrations of OMPI (+/- 10(-4) M) inhibit the self-assembly of microtubules in a cell free system. Low concentrations (+/- 10(-6) M) markedly enhance the polymerization rate of tubulin. Levamisole has no effect on tubulin polymerization. The effects of OMPI on microtubules in cells and in the polymerization system can be reversed by reduced glutathione, cysteine and dithiothreitol. The data indicate that OMPI interacts in a biphasic manner with microtubule formation probably through interaction with critical SH-groups on the tubulin molecule. It seems of interest to further investigate the hypothesis that the immunomodulating properties of levamisole are at least partially due to the formation of its metabolite (OMPI) which could enhance microtubule integrity and function in leukocytes.

The effects of thiol moiety of levamisole on both cellular and humoral immunity during the early response to a hapten-carrier complex

Cell-mediated reactions to the carrier and antibody-mediated reactions to the hapten were studied in guinea-pigs treated with a single i.v. injection of the thiol moiety of levamisole (DTC), before or after immunization with a hapten-carrier complex. The results show that a heavy dose of DTC induced delayed hypersensitivity reactions to the carrier and decreased antibody synthesis to the hapten. On the other hand, with a small dose of DTC no delayed hypersensitivity could be induced, but antibody synthesis to the hapten was depressed or enhanced, depending upon whether the injection was done before or after immunization. The mechanisms whereby DTC modulated the immune response are discussed.

Effect of levamisole on autologous rosette-forming cells in nude mice

Levamisole depresses the number of autologous rosette-forming cells (ARFC) in the spleen of nude (congenitally athymic) mice. Intravenous administration of 2.5 mg/kg of levamisole produces maximal depression. This effect appears 15 h after injection and is transient, partially disappearing after 48 hr. Dexamisole is devoid of this depressing activity. Thymopoietin, a thymic hormone, is also shown to lower the level of autologous rosette formation. These results suggest a stereospecific interference of levamisole with the maturation of immature T-cell precursors in a manner resembling the action of thymic hormones.