Biomedical subjects

L Lögdberg

Publications and source records attributed to L Lögdberg.

At least 19 recordsLinked to original sources

PubMed1995

Therapeutic efficacy of a polymyxin B-dextran 70 conjugate in experimental model of endotoxemia.

Numerous studies have suggested that lipopolysaccharide (LPS), a major component of the cell wall of gram-negative bacteria, is responsible for the initiation of gram-negative septic shock. Previously, others have designed therapeutic regimens to target the biologically active lipid A region of LPS by either neutralization of the biological properties of LPS or enhancement of clearance of this molecule. One such compound capable of neutralizing lipid A is the antibiotic polymyxin B. However, the clinical utility of polymyxin B is limited by its toxicity. We therefore covalently conjugated this antibiotic to the high-molecular-weight polysaccharide dextran 70, resulting in reduced toxicity of polymyxin B but retention of its endotoxin-neutralizing ability. The studies described in this report were designed to test the in vivo efficacy of this compound in an experimental animal model of gram-negative septic shock. Mice were administered graded doses of Escherichia coli or Pseudomonas aeruginosa along with D-galactosamine and the antibiotic imipenem. We had previously determined that antibiotic chemotherapy provides significant protection against E. coli-mediated lethality with smaller doses of bacteria; however, the antibiotic does not provide protection against larger doses of bacteria, but it is effective at killing the bacterial inoculum in vivo. Administration of the polymyxin B-dextran 70 conjugate provided significant protection when given with an antibiotic but was not effective by itself. A requirement for a pretreatment period prior to E. coli challenge was shown to depend upon the bacterial challenge dose. In other studies using this D-galactosamine sensitization model, we demonstrated that the lipid A-specific conjugate had no effect on lethality caused by staphylococcus aureus or tumor necrosis factor alpha. The results of these studies indicate that this compound is effective in preventing lethal gram-negative septic shock in mice and may be useful as a potential therapeutic agent in humans as well.

Animals↗

PubMed1994

Primate antibodies to components of the human immune system.

The feasibility to raise nonhuman primate antibodies against selected components of the human immune system was tested. The immunogens were whole cells (human T lymphocytes) or purified, recombinant human proteins (cytokines: TNF alpha or GM-CSF; soluble forms of cell surface antigens: sCD4 or sCD25). Significant immunizations, yielding functionally relevant antibodies, were readily achieved in rhesus monkeys, but, not surprisingly, may be less frequent in chimpanzees. The results suggest a general strategy for production of therapeutically useful MAB.

Animals↗

PubMed1991

Characterization of monoclonal anti-alpha 1-microglobulin antibodies: binding strength, binding sites, and inhibition of lymphocyte stimulation.

Eleven monoclonal antibodies (MoAb) directed against the immunoregulatory plasma glycoprotein alpha 1-microglobulin were characterized. The MoAb were produced in mice immunized with a mixture of alpha 1-microglobulin homologues from man, guinea pig, rat and rabbit. Using radioimmunoassay, western blotting, affinity chromatography, and Scatchard analysis, the affinities and binding sites of the MoAb were analysed. All antibodies were more or less cross-reactive, but most showed a major specificity for one or two of the alpha 1-microglobulin homologues. None of the antibodies was directed against the carbohydrate moiety of alpha 1-microglobulin. Six of the MoAb had high affinity for the antigen and four of these were directed towards the same part of the molecule though differing in their species specificity. Five showed lower affinity for the antigen and were mainly directed towards epitopes on other parts of the molecule. Only some of the antibodies could block the proliferation of lymphocytes induced by human alpha 1-microglobulin. The blocking efficiency of the different antibodies was similar when tested on the stimulation of human or mouse lymphocytes, suggesting that the same part of the alpha 1-microglobulin molecule is responsible in both species. The magnitude of blocking by the different MoAb was not related to their affinities, emphasizing the importance of where on the alpha 1-microglobulin molecule, rather than how strongly, they bind. The binding of the strongest blocking antibody was shown to be directed to a C-terminal peptide of rat alpha 1-microglobulin, indicating that this part of alpha 1-microglobulin is important for the mitogenic effects. Thus the panel of anti-alpha 1-microglobulin MoAb should be a valuable tool for structural and functional studies of alpha 1-microglobulin.

Alpha-Globulins↗

PubMed1990

An intriguing member of the lipocalin protein family: alpha 1-microglobulin.

The plasma protein alpha 1-microglobulin is a member of the lipocalin protein superfamily. In the last few years, the work on alpha 1-microglobulin has given unexpected and promising new results. Of particular interest are its molecular association with immunoglobulin A and with proteinase inhibitors, and its interactions with the immune system.

Alpha-Globulins↗

PubMed1990

Alpha 1-microglobulin is mitogenic to human peripheral blood lymphocytes. Regulation by both enhancing and suppressive serum factors.

Human alpha 1-microglobulin (alpha 1-m), a 26 kilodalton serum glycoprotein, was found to exert mitogenic effects on human peripheral blood lymphocytes (PBL) in serum-free medium. Purified T cells, but not B cells, responded with proliferation to alpha 1-m, but only in the presence of monocytes. The mitogenic activity could be partially neutralized by a mouse monoclonal antibody against alpha 1-m. The mitogenicity was species-specific, since alpha 1-m homologues from rats, guinea pigs and rabbits had no effect on human PBL. In a previous study, no effect of alpha 1-m was seen on PBL in the presence of 20% serum, and, therefore, we studied the influence of different concentrations of serum on the alpha 1-m-induced mitogenicity. Thus, human serum enhanced the mitogenic effects of alpha 1-m on human PBL at 1% concentration (v/v) and suppressed the effects at 10%. The suppressing effect of serum at 10%, but not the enhancing effect at 1%, seemed to be conserved among several species. To test the effect of serum proteins of different molecular sizes, human autologous serum was separated by gel chromatography on Sephadex G-200 into four fractions. Fractions 1 and 2 (roughly containing proteins larger than 100 kilodaltons) suppressed the mitogenic effects of alpha 1-m, while fractions 3 and 4 enhanced the stimulation by alpha 1-m, at 0.5% and concentrations above. It is concluded that the mitogenic effect of alpha 1-m on lymphocytes is regulated by several serum factors, both enhancing and suppressive, that does not have any proliferative effect of their own. It can be speculated that the balance between enhancing and suppressing co-factors in the blood determines the degree of the stimulation of lymphocytes by alpha 1-m. This is compatible with an immunomodulatory role for alpha 1-m, in spite of its relatively constant plasma levels in health and disease.

Alpha-Globulins↗

PubMed1990

Mitogenic effect of alpha 1-microglobulin on mouse lymphocytes. Evidence of T- and B-cell cooperation, B-cell proliferation, and a low-affinity receptor on mononuclear cells.

Human alpha 1-m microglobulin (alpha 1-m), a low molecular weight plasma protein, was found to exert mitogenic effects on mouse lymphocytes from lymph nodes and spleen. The stimulatory effects appeared to be strain-restricted: alpha 1-m induced a varying degree of proliferation of lymphocytes from three strains, whereas one strain responded poorly. Experiments with lymphocyte subpopulations showed only weak stimulatory effects of alpha 1-m on purified T and B lymphocytes cultivated alone. The addition of mitomycin-treated cells of the other subpopulation could not restore the proliferative responses in either T or B lymphocytes. Strong stimulations were recorded only when both T and B lymphocytes were present, indicating that the T and B lymphocytes cooperate to achieve the proliferation. However, FACS studies on cultured splenocytes indicated that the proliferating cells are predominantly B lymphocytes. These data extend our earlier findings of a mitogenic effect of alpha 1-m on guinea pig lymphocytes. Furthermore, results were obtained indicating the presence of a receptor on mononuclear cells. Iodine-labelled alpha 1-m was bound to mononuclear cells prepared from spleens, and the binding could be blocked by an excess of non-labelled alpha 1-m. Scatchard plotting of the data gave an equilibrium constant of 0.7 x 10(5)/M for the binding between alpha 1-m and the receptor. Together with the documented inhibitory activity of alpha 1-m on antigen-driven proliferation of lymphocytes, these results suggest an immunoregulatory role for alpha 1-m.

Alpha-Globulins↗

PubMed1990

Islet transplantation to the renal subcapsular space improves late complications in streptozotocin-diabetic rats.

Transplantation of isolated islets is a promising approach in the treatment of diabetes. We have examined the long-term effects on the late complications of islet transplantation in an experimental diabetes model in the rat. Diabetes was induced by streptozotocin (70 mg/kg i.v.) and the rats were treated with either insulin (daily injection of 40 U) or transplantation of 1,000 freshly isolated, hand-picked, islets into the left renal subcapsular space. Both islet transplantation and insulin treatment completely normalized the increased levels of blood glucose, urine volume and water intake that were observed in the diabetic rats. The decreased growth rate of the diabetic rats was almost normalized by both treatment protocols. As for late complications, after 3 months, all untreated diabetic rats had cataract. They also had swelling and vacuolation of renal tubular cells, and, consistent with this, very high levels of urinary beta 2-microglobulin excretion. Both islet transplantation and insulin treatment completely prevented these late complications. Thus, islet transplantation to the renal subcapsular space is in this experimental model as good as insulin treatment in treating the clinical signs of diabetes and in preventing diabetic complications in the eye and kidney.

Animals↗

PubMed1988

The complete amino acid sequence of rat beta 2-microglobulin.

The primary structure of rat beta 2-microglobulin (beta 2m) was determined. It is a polypeptide of 99 amino acids with the following sequence: IQKTPQIQVY SRHPPENGKP NFLNCYVSQF HPPQIEIELL KNGKKIPNIE MSDLSFSKDW SFYILAHTEF TPTETDVYAC RVKHVTLKEP KTVTWDRDM. The primary structure was determined by NH2-terminal sequence analysis together with sequence determination of one cyanogen bromide fragment and one tryptic peptide. Of other known beta 2m sequences, rat beta 2m is most homologous to mouse beta 2m (83% identity). The rabbit, human, and guinea pig sequences are more distant, with 24, 27, and 31% differences, respectively.

Amino Acid Sequence↗

PubMed1987

Structural relationship between alpha 1-microglobulin from man, guinea-pig, rat and rabbit.

Rabbit alpha 1-microglobulin was purified from the urine of sodium-chromate-treated animals by the use of gel chromatography on Sephadex G-100, affinity chromatography on concanavalin-A--Sepharose and ion-exchange chromatography on DEAE-Sephadex. Rabbit alpha 1-microglobulin had a molecular mass of 25.6 kDa on SDS/polyacrylamide gel electrophoresis. Alpha 1-microglobulin has previously been purified from the urine of humans, guinea-pigs and rats by similar methods, and the molecular masses of the four homologues were compared by SDS/polyacrylamide gel electrophoresis and gel chromatography in a denaturing medium. By these two methods the human homologue was 6 kDa and 3 kDa larger, respectively, than the other three proteins. Endoglycosidase F digestion of alpha 1-microglobulin, followed by SDS/polyacrylamide gel electrophoresis, revealed three protein bands in the human alpha 1-microglobulin sample, and only two bands in guinea-pig, rat and rabbit alpha 1-microglobulin, with a gap between each band of 2.6--2.9 kDa. The amino-terminal amino acid sequences of the four homologues were determined and between 72% and 81% homology was seen. The five amino-terminal amino acids present in the other species were missing in guinea-pig alpha 1-microglobulin. Our results indicate that human alpha 1-microglobulin is substituted with two N-linked oligosaccharides, while only one is attached to each of the other alpha 1-microglobulins, and that the extra glycosylamine-linked oligosaccharide in the human protein is attached to asparagine in position 17. Finally it is shown that all four homologues inhibit antigen stimulation of human lymphocytes, a finding which is consistent with our previous suggestion that the N-linked oligosaccharides carry the immunosuppressive activity of alpha 1-microglobulin.

Alpha-Globulins↗

PubMed1987

Cross-reacting monoclonal anti-alpha 1-microglobulin antibodies produced by multi-species immunization and using protein G for the screening assay.

In order to generate monoclonal antibodies (MAb) directed against the low molecular weight glycoprotein alpha 1-microglobulin, a BALB/c mouse was immunized with a mixture of human, guinea pig, rat and rabbit alpha 1-microglobulin homologues (multi-species immunization) and boosted several times. On day 194, the mouse splenocytes were fused to SP2/0 myeloma cells. The resulting hybridomas were screened for anti-alpha 1-microglobulin activity against the alpha 1-microglobulin mixture or against the individual homologues. For this screening, protein G (the newly described IgG-binding streptococcal protein) was used in a solid-phase radioimmunoassay. The binding of protein G to immobilized antigen-antibody complexes was enhanced by pre-incubation with rabbit anti-mouse immunoglobulin G. The result was a panel of nine established hybridoma lines, all producing unique monoclonal antibodies, of IgG1 or IgG2a class, to alpha 1-microglobulin. The antibodies were not only reactive in solid-phase radioimmunoassay, but they could also immunoprecipitate 125I-labeled soluble alpha 1-microglobulin. Moreover, they reacted specifically with the alpha 1-microglobulin band in Western blots of urinary proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Such monoclonal antibodies are potentially valuable reagents for the further characterization of alpha 1-microglobulin.

Alpha-Globulins↗

PubMed1986

Alpha 1-microglobulin is mitogenic for guinea pig lymphocytes.

Guinea pig alpha 1-microglobulin (alpha 1-m) was found to exert mitogenic effects on guinea pig lymphocytes, i.e. peritoneal exudate lymphocytes (PEL) or T lymphocytes from regional or mesenteric lymph nodes (LNL). On the other hand, spleen T lymphocytes did not respond to alpha 1-m. Stimulation of LNL required the presence of accessory cells. The stimulatory effect was strain-specific: alpha 1-m clearly induced proliferation of lymphocytes from Strain 2 guinea pigs, whereas Strain 13 lymphocytes responded poorly or not at all. Moreover, alpha 1-m inhibited antigen-driven proliferation of guinea pig lymphocytes. None of the effects described were species-specific, e.g. human alpha 1-m exerted similar effects on the guinea pig lymphocytes. These data indicate that alpha 1-m may be involved in the regulation of lymphocyte activation.

Alpha-Globulins↗

PubMed1986

Related bindings of aggregated beta 2-microglobulin, IgG Fab, kappa and lambda light chains to group A streptococci.

Aggregates of various mammalian beta 2-microglobulin (beta 2m) homologues were tested in binding experiments with group A streptococcal strains of different M types. The binding patterns obtained were similar, suggesting that evolutionarily conserved parts of the beta 2m molecule are responsible for the interaction with group A streptococci. An N-terminally abnormal beta 2m showed binding characteristics similar to those of normal human beta 2m, indicating that the amino-terminal does not participate in this interaction. Aggregates of human IgG Fab fragments, kappa chains and lambda chains, were also analyzed. Whereas several of the beta 2m-reactive M types did not interact with any of these aggregates, all strains binding aggregated Fab, kappa or lambda, also bound aggregated beta 2m. Strains of M types 4, 12, 23 and 53 bound all the tested proteins; M type 1 bound all but IgG Fab, whereas M types 46, 49 and 53 showed affinity for beta 2m and lambda chains only. In inhibition experiments, unlabelled aggregated beta 2m in excess completely blocked the uptake of radiolabelled aggregated IgG Fab, kappa and lambda chains. Conversely, Fab, kappa and lambda aggregates inhibited the binding of radiolabelled beta 2m aggregates. Our results indicate that the differences in reactivity recorded between beta 2m and IgG Fab, kappa and lambda chains, all structurally related, are quantitative rather than qualitative. Thus, a common binding structure for these aggregated proteins on group A streptococci appears probable.

Animals↗

PubMed1985

Rapid production of monoclonal antibodies to T lymphocyte functional antigens.

Brief immunization of rats with mouse lymphoid cells was combined with the rat/mouse hybridoma technology and functional hybridoma screening to yield a rapid method for the production of monoclonal antibodies (MAb) against functionally important T lymphocyte cell surface antigens. Two protocols were used. In one, rats were immunized once with mouse thymocytes followed by fusion and screening of the hybridomas for interference with the thymocyte co-stimulator (interleukin 1) assay. The resultant hybridomas included producers of MAbs against the L3T4-antigen (inhibitory), the Ly-1-antigen (stimulatory), and the Thy-1-antigen (inhibitory?). In the second protocol, rats were immunized twice with a T cell hybridoma. The resultant hybridomas were screened for inhibition of polyclonal T cell activation, induced by an anti-Thy-1 (MAb G7). A panel of MAbs against the Thy-1 antigen with different reactivity profiles was generated by this procedure. Most of the MAbs were of the IgM class. Short-term immunization may lead to less selection of response to highly immunogenic determinants than a protocol involving several boosters. Thus, this alternative may be useful for producing MAbs against rare or weakly immunogenic cell surface molecules, as suggested by the ease with which we were able to make MAbs against the L3T4-molecule.

Animals↗

PubMed1985

Role of the Ly 1 antigen in interleukin 1-induced thymocyte activation.

Interleukin 1 (IL 1), but not IL 2-induced thymocyte proliferation was augmented by monoclonal antibodies (mAb) against the Ly 1 antigen. The anti-Ly 1 mAb could also co-stimulate thymocytes with phytohemagglutinin (PHA) alone, mimicking the effect of IL 1. Moreover, overnight culture with PHA of thymocytes, but not of spleen T lymphocytes led to selectively enhanced expression of the Ly 1 antigen on the cell surface. Similar data were generated at the clonal level. Thus, a thymocyte hybridoma (22A6) could be stimulated to release IL 2 in response to PHA plus IL 1, but also to PHA plus anti-Ly 1 mAb. In addition, 22A6 exhibited enhanced cell surface expression of the Ly 1 antigen after overnight culture with PHA. These data suggest a critical role for the Ly 1 antigen in thymocyte proliferation, perhaps by serving as an IL 1-receptor.

Animals↗

PubMed1985

Role of the L3T4 antigen in T-cell activation. I. Description of a monoclonal IgM antibody to a distinct epitope (L3T4b) of the L3T4 antigen and its effect on interleukin 1-induced thymocyte proliferation.

This report describes a new rat monoclonal IgM/k antibody, monoclonal antibody (MAb) 2B6, which reacts with a cell surface antigen present on a subpopulation of both thymocytes (85%) and peripheral T lymphocytes (55-60%). The antigen recognized by MAb 2B6 has multiple properties in common with the L3T4 antigen, as defined by the recently described MAb GK1.5. Thus, MAb 2B6 and MAb GK1.5 give very similar flow cytometry staining patterns on thymocytes, purified spleen T cells and all tested T-cell hybridomas. Depletion of MAb 2B6-positive cells with antibody and complement led to simultaneous depletion of MAb GK1.5-positive cells, and vice versa. Depletion of Lyt 2-positive cells led to enrichment of both MAb 2B6- and MAb GK1.5-positive cells. Both MAb 2B6 and MAb GK1.5 immunoprecipitate the same pattern of cell surface molecules from detergent extracts of radiolabeled thymocytes, the main components being a 55-kDa and a 115-kDa band. We therefore conclude that MAb 2B6 reacts with the L3T4 antigen. Interestingly, MAb 2B6 and MAb GK1.5 do not cross-block and therefore most probably react with distinct epitopes on the L3T4 molecule. The determinant recognized by MAb GK1.5 is called L3T4a. We suggest that the determinant recognized by MAb 2B6 be named L3T4b. As MAb 2B6 was selected for its ability to inhibit the action of interleukin 1 (IL-1) in the thymocyte costimulator assay, it is likely that the L3T4 molecule is functionally involved in the events taking place during IL-1 induction of thymocyte proliferation.

Animals↗

PubMed1985

Role of the L3T4-antigen in T cell activation. II. Inhibition of T cell activation by monoclonal anti-L3T4 antibodies in the absence of accessory cells.

We have used two monoclonal antibodies (Mab) to the L3T4 antigen to reexplore the role of this molecule in the process of T cell activation. Both Mab (Gk1.5 and 2B6) were capable of inhibiting Con A-induced IL 2 production by a number of antigen-specific T cell hybridomas in an assay system that was free of major histocompatibility complex (MHC) class II antigen-bearing cells. The inhibition produced by the anti-L3T4 Mab was specific, because other Mab to cell surface antigens expressed on the hybridomas were without inhibitory effects. These studies rule out the possibility that the mechanism of inhibition by anti-L3T4 in this model is mediated by blocking interaction of L3T4 with MHC class II products. Taken together, these results and those of other groups of investigators, are most compatible with a dual function for L3T4 in T cell activation. L3T4 might first interact with MHC class II molecules or other molecules on target or accessory cells; L3T4 would subsequently transmit a signal that would regulate the activation process. Mab to L3T4 might exert inhibitory effects at one or both of these steps.

Animals↗

PubMed1984

Specific activity of carp antisera against beta 2-microglobulin (beta 2m) and evidence for a beta 2m homologue in carp (Cyprinus carpio).

Antisera against rabbit and human beta 2-microglobulin were produced in carp (Cyprinus carpio). These antisera were found to be specific for beta 2m, and detected beta 2m epitopes in various vertebrates including guinea-pig, cow, mouse, rat, dog, horse, cat, sheep, goat, parrot, chicken and frog. In addition, these antisera were also inhibited by an extract from oyster. The differences between the reactivity of these two antisera and the ability of the anti-rabbit beta 2m to distinguish between mouse and rat beta 2m's suggested that the carp itself carries beta 2m epitopes. This hypothesis was corroborated by the ability of a variety of mammalian anti-beta 2m antisera to induce a mitogenic response in carp leukocytes. Finally, a rabbit antiserum against dog beta 2m was shown to precipitate a low molecular weight molecule from carp leukocyte extract. This molecule is likely to represent the carp homologue of mammalian beta 2m.

Animals↗

PubMed1984

On the heterologous interaction between beta 2-microglobulin and the heavy chain of rat major histocompatibility complex class 1 antigens.

The heterologous interaction between beta 2-microglobulin (beta 2m) and rat major histocompatibility complex (MHC) (RT1) antigens was measured in a two-step binding assay consisting of binding of radiolabelled beta 2m to RT1 antigens and immunoprecipitation of beta 2m-RT1 antigen complexes with RT1 antisera. The effects of varying the concentrations of the three reactants involved were studied. The molecular events taking place in the two steps were analysed by gel chromatography. The beta 2m-RT1 antigen complex had the apparent size of albumin and reacted completely with specific alloantisera. RT1 antigens prepared from Wistar/Furth (RT1u) and Brown Norway (RT1n), respectively, both effectively bound heterologous beta 2m. The times for association and dissociation, respectively, at 37 degrees C, were of the same order, but dissociation was slightly slower. Association was markedly temperature-dependent and was considerably slower at low temperatures. All these processes were slower for RT1n than for RT1u antigens. The association constant for the interaction between RT1u antigens and 125I-human beta 2m was estimated by Scatchard analysis to be about 10(9) M-1. Contribution to the heterologous interaction by products from various rat MHC subloci (A, B, and C) was investigated by the introduction of sublocus-specific antisera in step 2. The reaction apparently involved neither class 2 antigens (sublocus B) nor the presumed rat Qa homologue (sublocus C). Classical class 1 antigens (sublocus A) clearly contributed to the binding. However, a monoclonal antibody against products from rat MHC class 1 genes only precipitated less than half of the RT1 antigen-complexed beta 2m. Thus, at least two RT1u class 1 alloantigen molecules seem to participate in the reaction. This, in turn, indicates that the rat genome may contain multiple class 1 genes, as is the case for most other mammals investigated.

Animals↗