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At least 703 records · Page 39Linked to original sources
PubMed1981

Role of accessory cells in B cell activation. IV. Ia+ accessory cells are required for the in vitro generation of thymic independent type 2 antibody responses to polysaccharide antigens.

It has been previously shown that the in vitro antibody response to TNP-Ficoll requires the presence of adherent accessory cells. In order to determine if this characteristic was unique to TNP-Ficoll or a general feature of the TI-2 antibody responses, responses to the polysaccharide antigens TNP-Levan and TNP-Dextran were studied. Also, it was determined if the functionally relevant accessory cell expresses Ia determinants. Passage of spleen cells over Sephadex G-10 abrogated the response to TNP-Levan and TNP-Dextran as well as to TNP-Ficoll. Addition of adherent accessory cells to the G-10 passed spleen cells reconstituted the response to all 3 antigens. Pretreatment of the adherent accessory cells with a specific anti-Ia serum plus complement abrogated the ability of these cells to provide accessory cell function in the responses to all 3 antigens. Thus, an Ia-positive adherent accessory cell is required for the generation of TI-2 antibody responses to these polysaccharide antigens. This raises the possibility that genetic restrictions may exist between the Ia-positive accessory cell and the lymphocytes involved in the responses to TNP-Ficoll, TNP-Dextran, and TNP-Levan.

Animals↗
PubMed1982

Enhancing activity of various immunoaugmenting agents on the delayed-type hypersensitivity response in mice.

Six immunoaugmenting agents were tested in the delayed-type hypersensitivity reaction (DTH) in normal BALB/c X DBA/2 mice. The agents tested, levan, lentinan, mannozym, maleic anhydride divinyl ether, polyriboinosinic-polycytidylic acid-poly-L-lysine, and highly purified L-cell interferon, gave significant increases in the DTH response above the sheep red blood cell control. The schedule of doses for each agent corresponded with previous experiments from this laboratory of the maximum natural killer cell activity, macrophage activation, and interferon induction. Highly purified L-cell interferon was capable of eliciting a significant DTH response when given 4 hr after the initial challenge with sheep erythrocytes. In addition, lambda-carrageenan, a macrophage-cytotoxic agent which can render the macrophage inactive, was found to suppress the DTH response to levels slightly above phosphate-buffered saline controls. The carrageenan-induced suppression of the DTH response could be abrogated by coadministration with immunoaugmenting agents to levels attained with the immunoaugmenting agents alone.

Adjuvants, Immunologic↗
PubMed1984

The effects of levan on the acute inflammatory response.

The fructose polymer levan has been shown to affect the accumulation of leucocytes in inflammatory lesions. The present study has investigated the effect of levan on experimental pleurisy induced by carrageenan and calcium pyrophosphate dihydrate (CPPD) crystals. Total pleural polymorphonuclear leucocyte counts and exudate volumes were significantly reduced by levan treatment. We were, however, unable to detect any effect on mononuclear cell numbers. Furthermore, levan treatment significantly reduced peripheral leucocyte numbers. The counter-irritant activity of levan was compared with that of a known counter-irritant, dextran. The ability of levan to reduce pleural polymorph numbers and exudate volume could not be accounted for totally by counter-irritation. Studies using an in-vitro leucocyte adhesion assay system indicate that levan affects leucocyte adhesion to vascular endothelium.

Animals↗
PubMed1984

Anti-immunoglobulin antibodies. V. Age-dependent variation of clones stimulated by polysaccharide TI-2 antigens in 129 and MRL mice spontaneously producing anti-gamma-globulin antibodies.

The nature of the immune response to two conventional polysaccharide thymus-independent (TI) antigens was investigated in two RF-producing mouse strains, the 129/Sv and MRL/1 pr, as well as in their normal congenic counterparts, 129/J and MRL +/+ animals. An age-dependent variation of clones specific for the TI-2 antigens bacterial levan (BL) and alpha 1, 3 dextran B1355 (Dex) was observed in 129/J mice. Surprisingly, the anti-BL and anti-Dex responses observed for young (1-mo-old) 129/Sv mice far exceeded those of their age-matched controls indicating an accelerated ontogenic development of the immune response to TI-2 antigens. A poor response was observed for both MRL +/+ and MRL/1 pr mice after immunization with BL. More importantly, MRL mice, unlike other H-2k, Igh.Ca strains, were unresponsive to Dex in CFA or saline. MRL mice, however, could respond to the T-dependent form of this antigen, Dex-KLH, suggesting that these mice lack the subset of B cells required to respond to TI-2 antigens. Finally, the most striking observation was the occurrence of isotype-specific RF subsequent to immunization with these antigens in animals prone to develop RF, as well as in aged animals that do not spontaneously produce RF.

Aging↗
PubMed1984

Direct antitumor effect of the polysaccharide levan in mice: effects of drug concentration and time and temperature of incubation.

In vitro treatment of Lewis lung carcinoma cells with the polysaccharide levan was shown previously to reduce the oncogenicity of these cells by acting on the cell membrane. In the present study the direct effect of levan on the tumorigenicity of Lewis lung carcinoma in C57BL male mice was tested at different doses and intervals and temperatures of incubation. A dose-dependent decrease in tumorigenicity was observed: Doses of 0.5, 1, and 2 mg levan/2 X 10(5) cells/0.2 ml reduced tumor incidence by 30, 50, and 70%, respectively. Some degree of inhibition was observed even with a dose of 0.004 mg. The inhibitory effect was rapid; 5 minutes of incubation resulted in the same reduction in oncogenicity as 60 minutes. Inhibition at 0 degree C was as effective as inhibition at 37 degrees C. The lack of temperature effect indicates that enzymatic activity probably is not involved. The data presented here, together with previous data, suggest that levan induces a physical, rather than a chemical, change in the affected tumor cells. The polysaccharide appears to be loosely, noncovalently bound to the cell membrane.

Animals↗
PubMed1983

Action of levan fructotransferase of Arthrobacter ureafaciens on levanoligosaccharides.

Levan fructotransferase of the bacterium Arthrobacter ureafaciens, which produces di-D-fructose 2,6':6,2' dianhydride (difructose anhydride IV) from levan by an intramolecular transfructosylation reaction, was purified to give a single protein band of pI 4.5-4.7 on isoelectric focusing. It had a molecular weight of 128,000 on gel-filtration on Sephadex G-200 and 60,000 on SDS-polyacrylamide disc gel-electrophoresis, suggesting that the enzyme is composed of two identical subunits. The shortest levanoligosaccharide chain required for the difructose anhydride IV formation was determined to be tetraose. TLC of the enzymic digest of a modified levanhexaose derived from levanhexaose by the reduction of the reducing end to an alditol residue with sodium borohydride gave the difructose anhydride IV spot, suggesting that the enzyme attacks the modified levanhexaose molecule from the direction of the non-reducing fructose end. The enzymic digests of levantetraose, -pentaose, and -hexaose as the substrate gave, in addition to the difructose anhydride IV spot, spots of oligofructans of lower mobility than the original substrate on TLC. From the digest of levantetraose, a hexaoligofructan and a smaller amount of a pentaoligofructan but no fructose were separated, indicating enzymic intermolecular levanbiosyl and fructosyl transfer reactions.

Arthrobacter↗
PubMedDate not supplied

[Levan synthesis by a Bacillus sp. culture].

A strain of Bacillus sp. was isolated which is an active producer of levan. The dynamics of the polysaccharide biosynthesis was studied depending on concentrations of sucrose in the medium. The amount of the synthesized levan was proportional to the concentration of sucrose ranging from 0.2 to 6%, being a maximum of 28.2 mg/ml in the medium containing 12% of sucrose. The presence of urea or ammonium sulfate in the medium stimulates the levan biosynthesis. A medium with pH 6.0--6.8 is optimal for the polysaccharide formation. Levan, synthesized by Bacillus sp., is a polysaccharide with the molecular weight more than 2 mln. Levansucrase is an induced enzyme, whose inductors are sucrose and raffinose.

Bacillus↗
PubMed1984

Serial passage of tumors in mice in the study of tumor progression and testing of antineoplastic drugs.

AKR lymphoma cells derived from spontaneous tumors were serially transplanted at identical inocula. The degree of malignancy and sensitivity to the polysaccharide levan and methotrexate were tested at each transfer by assessing the lag of development of primary and distant tumors and survival of mice. A progressive increase in malignancy, accompanied by a loss of sensitivity to levan, were observed following serial passage of the lymphoma. Sensitivity to methotrexate was not affected. It is reasoned that, since serial passages permit a longer exposure of the tumor cells to selective forces of the internal milieu of the organism, better reflecting the situation in a long-life span animal, spontaneous and serial-passage tumors could serve as models for cancer therapy in humans.

Animals↗
PubMed1983

Combined effect of levan and cytotoxic agents on the growth of experimental tumours in mice.

The combined effect of the polysaccharide levan (previously shown to exert a host-dependent as well as direct antitumoural activity) and the cytotoxic agents cyclophosphamide (CY), methotrexate (MTX), vincristine (VINC) and 5-fluoro-uracil (SFU) was studied in Lewis lung carcinoma and AKR lymphoma. Combined chemo- and immunotherapy was applied beginning on the day of tumour cell inoculation. Additive effects were obtained with the combined treatments, compared to single treatments, with all the combinations except MTX-levan in Lewis lung carcinoma, where the combined effect was synergistic. The additive effect was obtained with different doses and routes of chemotherapy, whether local or intraperitoneal. A 2 mg dose of CY combined with levan administered at daily doses of 10 mg, resulted in a 100% prevention of Lewis lung carcinoma growth. It is suggested that the levan may have two beneficial effects: it can exert an inhibitory effect on tumour growth and diminish the deleterious effect of cytotoxic agents on the immune system.

Animals↗
PubMed1983

An allotype linked gene that is associated with a negative or very low anti-phosphorylcholine response (PC) phenotype in wild mice (CNV).

In contrast to most inbred and wild mice, a population of wild mice recently isolated from a farm in Centreville, MD, and designated CNV produced no anti-phosphorylcholine (PC) antibodies (less than 1 microgram/ml) in response to immunization with the PC antigen Streptococcus pneumoniae (R36A) and gave 9 to 36 micrograms/ml anti-PC response to PC-KLH at 14 days after immunization. When another carbohydrate antigen, namely, bacterial levan, was used, CNV mice all gave high antibody titers. When CNV (PC-) mice were bred to inbred C.B20 (PC+) mice, 82% of the F1 and 76% of the F2 hybrids were surprisingly non-responders (PC-), which suggested that PC- gene(s) of CNV origin dominated the response to these antigens. The 18% PC+ phenotype in the F1 hybrids indicated possible heterozygosity of the PC genes controlling the PC- response in the CNV mice. Genetic studies on CNV mouse No. 378 supported this possibility. Analysis of the F2 data strongly suggest that two genes determined the PC- response, one of which was closely linked to the Igh-C allotype locus (chromosome 12). Hypothetically, we propose that CNV mice have two genes that cooperate but that sometimes act independently to express the PC- phenotype. Surprisingly, when F1 mice giving PC- phenotypes were back-crossed to C.B20, very few mice (18%) were PC-. This indicated that the PC- determining genes of CNV origin were not able to dominate immune responses in the presence of a larger number of C.B20 genes. This kind of expression may be regulated by other factors, such as clonotype competition and clonal dominance.

Animals↗
PubMed1980

Direct antitumor effect of high-molecular-weight levan on Lewis lung carcinoma cells in mice.

The polysaccharide levan exerted a direct effect on Lewis lung carcinoma cells in vitro. Tumor cells incubated with levan showed a pronounced decrease in oncogenic properties when inoculated sc in the syngeneic hosts (C57BL mice), although the viability of cells as determined by the trypan blue exclusion test was not diminished. The effect of pretreatment of inoculated mice with levan. Radiolabel incorporation into DNA, RNA, and protein was not affected in cells incubated with levan, but transport properties were selectively altered: Thymidine, uridine, and leucine transport was enhanced, whereas deoxyglucose transport was unchanged. The results indicated that levan exerted a direct antitumor effect on Lewis lung carcinoma cells in vitro.

Animals↗
PubMed1978

Modification of the tuberculin reaction by levan.

High molecular levan (polyfructoside) inhibits the skin tuberculin reaction in guinea pigs as judged by the degree of induration and erythema. The effect is dose-dependent. No effect on cellular infiltration was observed in histological studies. The lymph nodes of levan-treated animals were smaller and exhibited a much milder granulomatous reaction than those of non-treated animals.

Animals↗
PubMed1980

[Purification and properties of levansucrase of Gluconobacter oxydans L-1].

Levansucrase of G. oxydans L-1 which catalyzes the synthesis of the polysaccharide levan from the fructofuranosyl residues of sucrose has been isolated from the culture fluid and purified by chromatography on hydroxyapatite and gel-filtration on Sephadex G-100. The molecular weight of levansucrase as measured by DS-Na polyacrylamide gel electrophoresis is about 58000. The enzyme contains 25.86% of acidic amino acids, 13.74% of basic amino acids and 12.77% of aromatic amino acids. No cystine or cysteine residues were detected in the acid hydrolysate. The UV-absorption spectrum of the purified protein has a maximum at 280 nm and a minimum at 254 nm. The kinetic data suggest that levansucrase catalyzes levan formation, sucrose hydrolysis and sucrose glycosyl-free glucose exchange reactions. The initial rates of liberation of labelled glucose and labelled fructose during transfructosylation have been determined. Low molecular weight levans accelerate the rate of the polysaccharide formation and increase the ratio of the formed levan to free fructose.

Amino Acids↗
PubMed1981

Effect of immune response to sheep red blood cells on plasmacytoma MOPC 104 E.

BALB/c mice were given 1 x 10(6) MOPC 104E plasmacytoma cells i.v. to disseminate the neoplasm to various organs. Twenty-five days after implantation and at a time when the neoplastic B-cell clone was in the exponential growth phase, the mice were given i.p. injections of a mixture of antigens containing sheep red blood cells and levan. Each mouse was monitored simultaneously for immunoglobulin M (IgM) anti-dextran myeloma protein produced by the plasmacytoma and anti-sheep red blood cell hemolysin. The increase and decrease of these markers permit assessment of the expansion of the abnormal B-cell clone during the rise and fall of a normal B-cell clone in response to a specific antigen. The model was used to determine (a) the extent of the suppression of myeloma protein, (b) how long inhibition can be maintained, and (c) how soon it occurs after antigen is administered. The results showed that, as the IgM antibody response to sheep red blood cells begins to peak, it exerts a transient suppressive effect on either the MOPC 104E growth or on the cellular release of MOPC 104E IgM. The suppressive effect was noticeable 4 days after antigen administration for only 24 hr. These results indicated that plasmacytoma cells in vivo can recognize signals for either suppression of growth or release of the idiotypic MOPC 104E IgM and were not inconsistent with the view that myeloma may be the result of a defect in B-cell regulation.

Animals↗