T lymphocyte-derived demyelinating activity in multiple sclerosis patients in relapse

Supernatants of cultured T lymphocytes of multiple sclerosis patients were tested for a demyelinating activity in rat cerebellum explant cultures. Supernatants of unstimulated T lymphocytes in seven out of 10 multiple sclerosis patients in relapse produced demyelination when checked by phase contrast microscopy. Supernatants of unstimulated T lymphocytes from healthy subjects did not produce demyelination, but when T cells were stimulated by phytohaemagglutinin (PHA), 50% of tested supernatants produced demyelination, which was, however, never as advanced as in multiple sclerosis supernatant treated cerebellum cultures. The demyelinating activity proved to be heat labile. Gel filtration study revealed two fractions of the demyelinating activity 12.5-29.0 kD and 43.0-66.0 kD. The results suggest that lymphokines can be directly involved in the pathogenesis of demyelination in multiple sclerosis.

The magnitude of the spontaneous production of histamine-releasing factor (HRF) by lymphocytes in vitro correlates with the state of bronchial hyperreactivity in patients with asthma

In our previous studies we reported that lymphocytes from patients with asthma spontaneously produce histamine-releasing factor (HRF) in vitro. In an effort to examine whether spontaneous HRF production (SpHRF) by lymphocytes from patients with asthma is related to the state of bronchial hyperreactivity (BHR), 20 patients with mild to severe asthma were studied. Peripheral blood lymphocytes were cultured alone in a serum-free medium for 24 hours, and culture supernatant was assayed for HRF activity in two separate histamine-release tests with autologous basophils and normal basophils from known healthy donors. BHR was measured as bronchial reactivity to inhaled histamine and was expressed as a provocation concentration of histamine required to induce a 20% fall in FEV1 (PC20). The result of this study demonstrated that lymphocyte supernatant from all patients with asthma released significant amount of histamine from both autologous and normal basophils. Very high histamine release was usually induced by lymphocyte supernatant from severely ill patients who had PC20 less than 2 mg/ml. Statistical analysis demonstrated that the magnitude of the SpHRF significantly correlated (r = -0.86; p less than 0.001) with PC20. Since mast cell- and basophil-derived mediators have been implicated in the pathogenesis of BHR, high correlation between PC20 and SpHRF by lymphocytes suggests that the latter may contribute to the development of BHR. Further studies are required to disclose the exact relationship between SpHRF and BHR.

Multiple sclerosis: increased expression of interleukin-2 receptors on lymphocytes

The percentage of interleukin-2-receptor-positive peripheral blood lymphocytes in MS patients was significantly higher in acute relapse than in remission or in controls. After stimulation by phytohemagglutinin, the expression of interleukin-2 receptor on peripheral blood lymphocytes of MS patients was within the range of healthy controls, implying no general impairment of receptor expression. These results confirm other evidence that there is a small population of activated T lymphocytes in acute relapse of MS.

Studies on lymphokine-mediated demyelination in organotypic rat cerebellum in culture

Supernatants of peripheral blood lymphocytes (PBL), containing lymphokines, isolated from MS patients and healthy subjects were tested for demyelinating activity in organotypic culture of the rat cerebellum. PBL were isolated on Ficoll-paque gradient and cultures in RPMI 1640 medium for 72 h with or without phytohemagglutinin and Concanavalin A. Both stimulated and unstimulated PBL supernatants from MS patients consistently demyelinated cerebellum cultures. The supernatants of unstimulated PBL from healthy subjects did not produce demyelination, however, slight effect was present in the cultures treated with PBL stimulated supernatants. The results indicate that lymphokines might be involved in demyelination in MS.

Scavenger activity in monocyte-derived macrophages from atherothrombotic strokes

Foam cells are lipid-laden macrophages derived primarily from circulating mononuclear cells and are a characteristic feature of atheromatous lesions. The exact role of these foam cells in the pathogenesis of atherosclerotic lesions remains uncertain, but one potential function is to take-up and process excess interstitial arterial lipoproteins, suggested by their extraordinary ability to engulf enormous quantities of modified low density lipoproteins by the so-called "scavenging pathway." To test this possibility, monocytes from 15 atherothrombotic brain infarct patients and age and sex matched controls were isolated and cultured for 7-8 days in 20% normal serum. The monocyte-derived macrophages were investigated for their ability to bind, internalize and degrade both native and modified (acetylated) LDL labelled with 125Iodine. While native LDL was metabolized similarly, stroke macrophages displayed significantly reduced ability to scavenge modified LDL. These findings suggest that insufficient processing of interstitial arterial cholesterol by monocyte-derived macrophages may contribute to the aggravation of atheroma formation. This inadequacy is likely further compromised by reduced levels of serum high density lipoprotein since the absence of a cholesterol-acceptor will promote the slow but continued accumulation of lipids and the formation of foam cells.

Studies on histamine releasing factor (HRF) of human, murine and guinea-pig origin

There has been the lack of small animal models for the studies of histamine releasing factor (HRF). We have found that HRF produced in vitro by lymphocytes of asthmatic patients can act independently from the animal species and induces histamine secretion from mouse peritoneal mast cells. We also found, that spleen cells derived from normal as well as from sensitized mice and guinea-pigs are able to generate HRF in vitro, when cultured in suitable conditions. HRF of mouse and guinea-pig origin released histamine from homologous mast cells in vitro and its activity was enhanced when spleen cell cultures were stimulated with specific antigens or non-specific mitogen.

Bacterial antigens stimulate the production of histamine releasing factor (HRF) by lymphocytes from intrinsic asthmatic patients

Lymphocyte from 12 intrinsic asthmatic patients and 10 healthy controls were studied for their capability to produce histamine releasing factor (HRF) in vitro. Spontaneous HRF production was measured by culturing the lymphocytes alone for 20 h. In another set of experiments lymphocytes were first preincubated separately with phytohaemagglutinin, antigens of Haemophilus influenzae, Streptococcus viridans, Staphylococcus sp. and Neisseria catarrhalis for 4 h then carefully washed three times and cultured alone for an additional 16 h. Cell-free supernatant was assayed for histamine releasing activity using basophils from healthy donors. It was observed that lymphocytes from intrinsic asthmatic patients spontaneously produced HRF. The production of this lymphokine was enhanced following preincubation of lymphocytes with phytohaemagglutinin or bacterial antigens. Results of skin test with bacterial antigens did not correlate with the magnitude of the production of HRF by lymphocytes. At gel chromatography over Sephadex G-75 bacterial antigen-stimulated lymphocyte supernatant revealed two peaks of HRF activity in the molecular weight ranges 35,000-50,000 and 3,000-7,000.

A lymphocyte-derived histamine-releasing factor in asthmatic patients. III. Further studies

Peripheral blood lymphocytes from atopic asthmatic patients cultured overnight (16 hours) produced a novel lymphokine-histamine releasing factor (HRF) in the culture supernatant. Activity of this lymphokine has been tested in the basophil histamine release test. Supernatant from unstimulated lymphocytes released 29% histamine from basophils. A short incubation of lymphocytes with skin test-positive allergens (grass, mite) enhanced the generation of HRF. Skin test-negative allergens had no effect. HRF appeared in the supernatant as early as four hours after the start of the culture and its production level remained high even at 48 hours. Gel-filtration with Sephadex G-75 revealed an apparent molecular weight for HRF in the range of 10,000 to 15,000. HRF is relatively heat stable at 56 degrees C.

Enhancement of cholesteryl ester metabolism in cultured human monocyte-derived macrophages by verapamil

The effect of the Ca2+ entry blocker, verapamil, on the biosynthesis of cholesterol and the metabolism of low-density lipoprotein (LDL) was studied in cultured human monocyte-derived macrophages. Addition of verapamil (50 microM) of monocyte-derived macrophages enhanced 125I-LDL and 125I-labelled acetyl-LDL binding and internalization, and increased [2-14C]acetate incorporation into cholesterol. Since higher levels of LDL and modified lipoproteins may be implicated in atherogenesis, the more efficient processing of these lipoproteins by monocyte-derived macrophages in the presence of Ca2+ blocker warrants further assessment for its potential as an antiatherogenic agent.

A mononuclear cell-derived histamine releasing factor in asthmatic patients. II. Activity in vivo

In an attempt to study the role of lymphokines in asthma, lymphocytes from asthmatic patients were stimulated in vitro with skin test-positive allergen (dust mite) or with non-specific mitogen-phytohaemagglutinin for 4 h, then washed carefully and cultured alone for 16 h. Cell-free supernatants were subsequently collected and applied in the basophil histamine release test in vitro and in bronchial provocation test and skin prick test in vivo. Supernatant of non-stimulated lymphocytes from asthmatic patients released significant amounts of histamine from basophils. Stimulation of lymphocytes with specific allergen or phytohaemagglutinin augmented the supernatant-induced histamine release. Lymphocyte supernatants from the majority of patients also induced bronchoconstriction and elicited skin wheal and flare reaction in vivo.

Action of the human lymphokine histamine releasing factor on mouse peritoneal mast cells

Histamine releasing factor (HRF)--a human lymphokine--has been shown previously to release histamine from basophils in vitro. In this paper we show that HRF acted across the species barrier and released histamine from mouse peritoneal mast cells. This response was dose-dependent. Mast cells from both sensitized and non-sensitized mice were equally susceptible to the action of HRF. We observed synergistic action of HRF with specific allergen (ovalbumin) or HRF with anti-IgE antibody in releasing histamine from mast cells. Preincubation of mast cells with calcium ion chelating agent ethylenediaminetetraacetic acid (EDTA) or disodium cromoglycate induces only a small inhibition of histamine release caused by HRF. We conclude that histamine release from mouse peritoneal mast cells can serve as an in vitro test for the assay of human HRF.

A mononuclear cell derived histamine releasing factor (HRF) in asthmatic patients. Histamine release from basophils in vitro

Mononuclear cells from asthmatic patients produced a histamine releasing factor (HRF). Mononuclear cells produced this factor in culture spontaneously but significantly much more following specific allergen stimulation. This factor released histamine from both sensitized and unsensitized basophils in vitro. Mononuclear cells from healthy subjects produced HRF only after nonspecific mitogen/phytohemagglutinin stimulation. Asthmatic patients on immunotherapy with essential benefits failed to produce HRF.

Complement in allergen-induced bronchospasm in house-dust RAST negative asthmatic patients

We studied a group of asthmatic patients with aspirin intolerance who were RAST-negative for house-dust and Dermatophagoides-pteronyssinus despite having positive skin tests and positive inhalation tests to these allergens. Total haemolytic activity (CH50), C3, C4 and C3PA were measured after allergen-induced bronchospasm in these patients and also in a group of RAST-positive asthmatic patients taken as a control group. We did not find any change in complement level after allergen-induced bronchospasm in both groups of patients.