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Biomedical subjects

L Chedid

Publications and source records attributed to L Chedid.

At least 181 records · Page 10Linked to original sources
PubMed1977

Enhancement of nonspecific immunity to bacterial infection by cord factor (6,6'-trehalose dimycolate).

The capacity of mycobacteria to enhance the nonspecific resistance of mice to bacterial infections was related to the presence of cord factor. After enzymatic digestion and delipidation, cell walls lost their immunopotentiating activity, which was restored, however, by the addition of cord factor. Cord factor administered alone protected mice effectively against virulent organisms unrelated to mycobacteria. Moreover, although this glycolipid is usually injected as a solution in mineral oil, our data show its effectiveness when administered in metabolizable peanut oil or even as a suspension in water. Since cord factor is a chemically well-defined molecule (6,6'-trehalose dimycolate), this glycolipid should constitute a new and useful tool for the investigation of nonspecific immunity to infection.

Animals↗
PubMed1977

Chemically defined bacterial products with immunopotentiating activity.

The adjuvant activity of two chemically well-defined bacterial products is reviewed: (1) lipopolysaccharides of gram-negative bacillis and their acylated detoxified derivatives, and (2) mycobacterial water-soluble fractions and synthetic analogues. Water-soluble adjuvant can substitute for mycobacteria in Freund's adjuvant, but if it is administered in saline, it has little activity. In contrast, lipopolysaccharide under the same conditions markedly increases the humoral antibody response. However, the use of lipopolysaccharide is limited by its toxicity. Water-soluble adjuvant treated with phthalic or succinic anhydride was shown to be an adjuvant when administered in saline. Furthermore, synthetic M-acetyl-muramyl-L-alanyl-D-isoglutamine also increased the humoral immune response when given in aqueous medium instead of in the usual water-in-oil emulsion. This compound, which has a small molecular weight, is not mitogenic, immunogenic, or toxic in mice, and was shown to have adjuvant activity even when given by the oral route.

Adjuvants, Immunologic↗
PubMed1977

Inheritance of lipopolysaccharide-enhanced nonspecific resistance to infection and of susceptibility to endotoxic shock in lipopolysaccharide low-responder mice.

In a previous study, we demonstrated that lipopolysaccharide (LPS) and other bacterial immunostimulants, in contrast to their activity in a closely related high-responder subline, failed to elicit nonspecific resistance in LPS low-responder mice against Klebsiella pneumoniae infection. To investigate the type of inheritance controlling the LPS-induced nonspecific resistance to infection, the present study was performed in low- and high-responder C3H sublines and in F1 and F2 hybrids. In addition, F1 mice were backcrossed to each parental type. Inheritance of susceptibility to endotoxin was also tested in both sublines and their hybrids and backcross progeny. For these latter assays, mice were previously adrenalectomized because removal of this gland considerably enhances their sensitivity. Our present findings are consistent with the hypothesis that LPS enhances nonspecific resistance to infection and that susceptibility to endotoxin shock in the absence of corticoids may be determined by a single autosomal dominant gene.

Adrenalectomy↗
PubMed1977

Nocardia water-soluble mitogen and lipopolysaccharide. Comparative study of two adjuvants and B-cell mitogens in mice.

The activity of Nocardia water-soluble mitogen (NWSM) and LPS were compared in several experimental systems, since both compounds are B-cell mitogens and polyclonal activators in vitro. The results reported here demonstrated that NWSM like LPS also has a strong adjuvant activity in vivo if administered in saline with a strong antigen (heterologous red blood cells) or even with a weak immunogen such as theta alloantigen. However, in contrast to LPS, NWSM administered to mice failed to induce in vivo proliferation of lymphocytes, polyclonal activation and PFC against syngeneic bromelain-treated erythrocytes and thymocytes. It is possible therefore, that different mechanisms may be responsible for adjuvant activity of NWSM and LPS.

Adjuvants, Immunologic↗
PubMed1976

Adjuvant disease induced by mycobacteria, determinants of arthritogenicity.

Genetic, endocrine and immunological factors are probably involved in adjuvant polyarthritis. The nature of the vehicle and of the mycobacterial components administered also has a major influence. It was originally assumed that arthritogenicity and adjuvanticity of mycobacterial fractions such as wax D were intimately related. Our previous findings showed that the water soluble adjuvant (WSA) of M.smegmatis which could substitute for mycobacterial cells in Freund's complete adjuvant and induce delayed hypersensitivity was not arthritogenic in the Wistar rat. We have since observed that auto-immune diseases could be elicited by WSA. Therefore experiments were repeated using the very susceptible Lewis strain. The activity of cord factor and of various mycobacterial preparations suspended in mineral or in peanut oil was also evaluated in mice and in normal or hypophysectomized rats. Our present findings confirm the absence of arthritogenicity of WSA in the Lewis strain. They also indicate that cord factor with WSA does not suffice to induce a generalized adjuvant disease, but that a mycobacterial component which could be susceptible to lysozyme treatment is required also. However, the local inflammation of the injected limb was produced by a preparation of cord factor administered in mineral or even in peanut oil. This was observed in normal or hypophysectomized rats and in Swiss mice which were not susceptible to the generalized disease.

Animals↗
PubMed1976

Modulation of the immune response by a synthetic adjuvant and analogs.

N-Acetylmuramyl-L-alanyl-D-isoglutamine increases the humoral immune response of mice when given in aqueous media instead of the usual water-in-oil emulsions. Moreover, this compound is adjuvant active even by the oral route. In view of studying the relation between chemical structure and biological activity, several synthetic analogs were tested. The immune response could be modulated according to chemical modifications, and the synthetic analog with D- in place of L-alanine was shown to inhibit the immune response.

Adjuvants, Immunologic↗
PubMed1976

Stimulation of lymphocytes by purified protein derivative: suppression by cells from human vaccinated with Bacille Calmette-Guérin.

Specific stimulation of thymus-derived cells by purified protein derivative or tetanus toxoid was inhibited by autologous lymphocytes. The lymphocytes, which were collected from healthy humans who had been vaccinated with bacille Calmette-Guérin were purified on nylon columns after removal of cells that form rosettes with sheep erythrocytes. The degree of purification of the lymphocytes was controlled by appropriate techniques.

B-Lymphocytes↗
PubMed1976

Nonspecific resistance to infection induced in mice by a water-soluble adjuvant derived from Mycobacterium smegmatis.

The effect of a nontoxic, water-soluble adjuvant (Neo-WSA) from delipidated cells of Mycobacterium smegmatis on the susceptibility of mice to infection with four challenge organisms was studied. An intravenous dose of 1 mg of Neo-WSA per mouse 24 hr before challenge enhanced resistance to infection with a fungus (Candida albicans), a gram-negative bacterium (Klebsiella pneumoniae), and a gram-positive bacterium (Streptococcus pneumoniae). Protection by Neo-WSA was not significant when the mice were challenged with a malarial parasite. Plasmodium berghei. When 1 mg of Neo-WSA was given intravenously to mice 10 min before challenge with C. albicans, protection was significant, but when the same dose was given two or six days prior to challenge, mice were not protected. The concentration of iron in serum had not changed significantly 1 or 24 hr after the intravenous injection of 1 mg of Neo-WSA. Thus Neo-WSA is capable of inducing nonspecific resistance to certain experimental infections in mice. The protection afforded by administration of Neo-WSA 10 min before challenge, the lack of protection afforded by administration of Neo-WSA six days before challenge, and the lack of significant change in the serum iron concentration clearly separate this compound from bacterial endotoxins, which are classical inducers of nonspecific resistance to infection.

Adjuvants, Immunologic↗
PubMed1976

Role of B-lymphocytes in nonspecific resistance to Klebsiella pneumoniae infection of endotoxin-treated mice.

Lipopolysaccharides (LPS) of gram-negative bacilli are known to protect mice against unrelated bacterial infections and to be nonspecific mitogens of murine bone marrow-derived (B-) lymphocytes. For assessment of the role of these cells in the mechanism of LPS-induced resistance to infection with Klebsielia, various nontoxic mitogens were assayed. In contrast to LPS or lipid A, the nontoxic mitogens did not protect mice. Experiments were also performed with LPS in nude mice and in mice treated with immunosuppressants. Stimulation by LPS was decreased after administration of hydrocortisone or cyclophosphamide under conditions that inhibited the in vitro activation of lymphocytes by mitogens. Moreover, nude mice and mice treated with 6-mercaptopurine were more resistant to Klebsiella than were control mice.

Animals↗
PubMed1976

Failure of endotoxin to increase nonspecific resistance to infection of lipopolysaccharide low-responder mice.

In vitro and in vivo responses to lipopolysaccharide (LPS) and various other bacterial immunostimulants were compared in c3H/He low-responder mice. The principal findings were as follows. (i) Their splenic lymphocytes were stimulated by various gram-negative mitogens such as an Escherichia coli peptidoglycan, a detoxified derivative of LPS, and even endotoxins extracted by trichloroacetic acid that are known to contain protein; spleen cells of these mice were also transformed by two other B-cell mitogens extracted from acid-fast organisms. (ii) Their macrophages were refractory to LPS and weakly responsive to a mycobacterial prepartion. (iii) LPS failed to elicit nonspecific resistance in these mice against Klebsiella pneumoniae infection. (iv) Endotoxin extracted by trichloroacetic acid and a mycobacterial preparation that could increase nonspecific resistance to infection in other strains did not protect C3H/He mice against a challenge by K. pneumoniae, although both prepartions could evoke nonspecific responses of B cells in this low-responder subline.

Animals↗
PubMed1976

Presence and subcellular localization of two distinct mitogenic fractions in the cells of Nocardia rubra and Nocardia opaca: preparation of soluble mitogenic peptidoglycan fractions.

Fractionation of cells of Nocardia rubra and Nocardia opaca led to the separation of the cell wall and a "cytoplasmic" fraction. Both fractions were mitogenic for the splenocytes of AKR and nude mice and of rabbits. The peptidoglycan was the active part of the cell wall fraction. The products solubilized by the action of Streptomyces albus G peptidases on the peptidoglycan of N. rubra were mitogenic, but the products solubilized by lysoyme were not. Tentative structures are proposed for these fractions. The most active part of the cytoplasmic fractions could be sedimented by centrifugation and seemed to be related to the cytoplasmic membrane.

Animals↗
PubMed1976

Activity in saline of phthalylated or succinylated derivatives of mycobacterial water-soluble adjuvant.

A water-soluble fraction (WSA) of the cell wall can substitute for mycobacterial cells in Freund complete adjuvant. However, when WSA is administered in saline instead of in a water-in-oil emulsion, its adjuvant activity is very weak, and under certain experimental conditions it can even inhibit the humoral immune response. The data reported in the present study show that after treatment by phthalic or succinic anhydride the adjuvant activity of WSA was markedly changed, since high levels of circulating antibodies were produced when these derivatives were administered with an antigen in an aqueous medium. Moreover, the antigenic determinants of WSA were modified and acylated WSA had no tuberculin-like activity.

Acylation↗
PubMed1976

Cell suppression in PPD-induced blast specific response of human peripheral blood lymphocytes.

Secific stimulation of T-cells by PPD was inhibited by their autologous B cells. This inhibition was obtained with B cells separated either by depletion of E-RFC or by elution, with human IgG of lymphocytes bound to Sephadex beads coated with rabbit antibodies anti-human Fab fragments. The suppression was proportional to the number of B cells added to 10(6) T cells incubated with PPD and as previously reported was more marked in the case of B or T cells from BCG-vaccinated subjects with negative skin tests. The suppressive phenomenon required viable B cells and was inhibited by cycloheximide but was not altered by pretreatment of suppressor cells with actinomycin D or colchicine. It seems that B-suppressor cells interfere with recognition of PPD by T cells rather than with the proliferative phase of the specific blast response. Using various surface markers (i.e. Ig, C3 and Fc receptors) it was shown that the suppressor cells represent a subset of Ig-bearing B cells which do not carry Fc receptors.

Antigens↗
PubMed1976

A human T-independent B lymphocyte mitogen extracted from Nocardia opaca.

Nocardia water soluble mitogen (NWSM), a mitogen specific for mouse and rabbit B cells, activates blood, spleen, and tonsil lymphocytes from all the humans tested. Evidence is presented that it acts selectively on human B lymphocytes. B-enriched cells were recovered from anti-Ig-coated Sephadex columns or after elimination of E rosette-forming cells: they were able to incorporate tritiated thymidine when they were cultivated in the presence of NWSM whereas they were not activated by PWM. Conversely T-enriched suspensions did not respond to NWSM although they were able to be stimulated by PHA and PWM. Moreover, the response to NWSM remained unchanged after T cells had been killed by anti-HTLA serum and complement and disappeared after B cells had been killed by anti-HBLMA serum. After stimulation by NWSM, the number of direct plaque-forming cells to HRBC, LPS, and TNP was significantly increased, showing a polyclonal activation of human B lymphocytes. Since no evidence of T cell help for B cell activation has been found, NWSM thus appears to be a T-independent human B lymphocyte mitogen.

B-Lymphocytes↗
PubMed1975

[Increase of immune response by administration of metabolizable vegetable oil emulsions].

Though highly efficient, Freund's adjuvant has serious limitations because it contains mineral oil and isomannide monooleate emulsifier (arlacel A). The present study describes the conditions under which a stable water in oil emulsion can be produced by using metabolizable peanut oil with arlacel. When mycobacteria are added, a potent emulsified oil adjuvant is obtained which increases the immune response to BSA and to influenza vaccine.

Adjuvants, Immunologic↗
PubMed1975

Comparison between macrophage activation and enhancement of nonspecific resistance to tumors by mycobacterial immunoadjuvants.

It has repeatedly been observed that various bacterial preparations could increase the host's resistance to tumors. It has also been shown that after nonspecific activation by BCG (bacillus Calmette-Guérin), peritoneal macrophages could inhibit in vitro the growth of neoplastic target cells. In the present study a fraction extracted from Myobacterium smegmatis and referred to as interphase material was tested in view of measuring its ability to activate macrophages in vitro and in vivo. This preparation was previously shown to protect mice against a syngeneic leukemia and to increase the immune response of the guinea pig. Other water-soluble adjuvants devoid of demonstrable antitumor activity in vivo were also assayed. The results argue in favor of a correlation between adjuvant activity and the capacity of activating macrophages. Moreover, interphase material administered in vivo consistently induced stronger and more persistent stimulations of macrophages than the other preparations assayed.

Adjuvants, Immunologic↗