Suppression of reaginic antibodies

Macromolecular Prodrugs of 5-Fluorouracil. 1: Synthesis and Hydrolytic Stability

The hydroxyl groups of poly(ethylene glycol), dextran and poly-[N5-(2-hydroxy-ethyl-L-glutamineI were activated using the 4-nitrophenyl chloroformate method. The resulting phenyl carbonate groups reacted quantitatively with the primary amine groups of oligopeptides with 2-(5-fluorouracil-1-yl) glycine ethyl ester moiety as C-terminus. Following this procedure, 5-fluorouracil-polymer conjugates with peptide chains of different amino acid sequences and configurations were synthesized. The conjugates showed a good hydrolytic stability in buffer solutions of pH 7.4 and 5.5, as well as in calf serum, which indicated good stability of the polymer-drug linkage in the blood.

Polyethylene glycol reduces the inflammatory injury due to cold ischemia/reperfusion in autotransplanted pig kidneys

BACKGROUND

The conditions of storage of donor kidney may influence the deleterious consequences of ischemia/reperfusion injury (IRI) on delayed graft function. Since polyethylene glycol (PEG) can protect renal tubule cells against cold injury, we tested the effects of adding PEG 20 kD to ice-cold preservation solutions on the IRI of autotransplanted pig kidneys.

METHODS

The pigs' left kidneys were removed, cold-flushed with University of Wisconsin (UW) or simplified high K+ or high Na+ solutions with or without 30 g/L PEG 20M and stored for 48 hours at 4 degrees C. The kidneys were then autotransplanted and the contralateral kidneys were removed. Kidney biopsies were then performed and renal function parameters were analyzed over 8 to 12 weeks following surgery.

RESULTS

The kidneys cold-flushed with PEG-supplemented solutions on day 7 post-transplantation were better preserved and exhibited less marked nuclear tubular cell damage than the kidneys cold-flushed with the UW solution alone. PEG also almost completely inhibited the overexpression of major histocompatibility complex class II that was detected in epithelial tubule cells from kidneys cold-flushed with the UW solution. PEG also significantly reduced the number of CD4+ T lymphocytes and limited the infiltration of macrophages/monocytes and the progression of interstitial fibrosis in the 8- to 12-week post-transplanted kidneys. Moreover, pigs autotransplanted with kidneys flushed with PEG-supplemented solutions had the best renal function and the lowest levels of proteinuria.

CONCLUSIONS

These findings indicate that PEG inhibits the early inflammatory response due to IRI, improves renal function, and may prevent the progression of interstitial fibrosis in the long-term autotransplanted pig kidney.

Protection of autotransplanted pig kidneys from ischemia-reperfusion injury by polyethylene glycol

BACKGROUND

Ischemia-reperfusion injury (IRI) is often responsible for graft rejection and leads to delayed graft function of cadaveric kidneys. We have shown that adding polyethylene glycol (PEG 20M) to the preservation solutions helps protect isolated perfused pig kidneys against cold ischemia and reperfusion injury.

METHODS

We compared the effects of adding PEG to a simplified high-K+ perfusion solution of cold-stored kidneys to Euro-Collins or University of Wisconsin solutions on the function of reperfused autotransplanted pig kidneys. The left kidney was cold-flushed with the preservation solutions and stored for 48 hr at 4 degrees C before reimplantation. Creatinine clearance and fractional excretion of sodium were analyzed 2 days before surgery and over 7 days after transplantation. Histological sections were obtained 40 min after reperfusion and on day 7 after surgery.

RESULTS

Adding PEG to the perfusate significantly reduced IRI from autotransplanted pig kidneys. Creatinine clearance was significantly higher and fractional excretion of sodium was significantly lower in pigs transplanted with kidneys cold-flushed with PEG-supplemented perfusate than in those flushed with Euro-Collins or University of Wisconsin solutions. PEG supplementation also better preserved the integrity of kidney cells and markedly reduced interstitial cell infiltrates.

CONCLUSION

PEG protects against IRI and reduces early cellular inflammation. PEG may impair the recruitment and migration of leukocytes into retransplanted pig kidneys. Cold preservation of donor organs with PEG-supplemented solutions may therefore help limit IRI in human renal transplantation.

Evidence of a common regulation of IgE and IgG-subclass antibodies in humans during immunotherapy

Based on a 3-year prospective study of 20 pollen-allergic patients, where a detailed analysis of the IgE, IgG1 and IgG4 immune response was performed, we propose that a common regulatory mechanism exists between the IgE and IgG1 synthesis and between IgE and IgG4 synthesis during immunotherapy. It was found that the IgE immune response to a number of antigens was quantitatively diminished during the period of immunotherapy when IgG1 was present early (week 12), and for other antigens there was a rise in IgE without an early IgG1 antibody response. Additionally, it was found that for some antigens a rise in IgE antibodies was contrasted by a fall in the IgG4 antibody response and for other antigens the opposite was true, indicating a regulatory mechanism between the IgE and the IgG4 synthesis. A statistical analysis showed that these findings were statistically significant at the 0.01% level for the IgE/IgG1 relationship and at the 0.05% level for the IgE/IgG4 relationship. These findings could have implications for future immunotherapy regimens.

Cellular and molecular mechanisms of B lymphocyte tolerance

A paradox of immunology is that the immune system is distributed so widely in the body, as a large number of cells that discharge most of their effector functions as single cells; but, at the same time, the elements of the system are so very interdependent, not only via specialized cell clusters and microenvironments, but also by mobile feedback loops, cellular and molecular. The end result is that one cannot really understand one element of the system without understanding every other, at least to a degree. Certainly, tolerance cannot be isolated from immune activation, nor B cell from T cell tolerance, rendering the task of the reviewer somewhat thankless. This being said, the last few years have seen wonderful progress in our grasp of B cell tolerance, to which the transgenic revolution has contributed a great deal. The fact that B cell tolerance exists as an important component of self-tolerance has been firmly established, as have the limits of the process in terms of both the survival of low-affinity antiself clonotypes and the question of location and concentration of antigen required for tolerance induction. Two processes have been identified as key alternatives: clonal abortion/maturation arrest/deletion and induction of clonal anergy. The latter requires a less strong Ig receptor crosslinking signal, may be partial, and is reversible. Recognition of these facts has prompted both experimentation and speculation on possible functions of the anergic cell. One unsatisfactory area, which we have not addressed because nothing like a consensus has been reached, is T cell-mediated suppression and its possible effects on tolerant states, including anergy induction in B cells. The phenomenology of suppression is too striking to sweep under the carpet, and suppressor T cell memory in particular (Adelstein et al., 1990) requires much more investigation; however, suppression has not been shown to play a major role in any of the best-studied transgenic models. These can readily be explained on the basis of direct interactions between the B cell target for abortion or anergy and the self antigen in question. The biochemical basis of discrimination between immunity and tolerance has also progressed, but not as fast. This is understandable, as so many signaling pathways have to come together for full immune induction, and as immaturity of the signal transduction pathway plays a profound role that must be studied in normal cells, with all the attendant difficulties of cell separation.(ABSTRACT TRUNCATED AT 400 WORDS)

A computational approach to the description of individual immune responses. IgE and IgG-subclass allergen-specific antibodies formed during immunotherapy

Detailed evaluation of the IgE and IgG-subclass immune response during immunotherapy can now be performed by crossed radio immunoelectrophoresis (CRIE). Some new concepts are introduced facilitating the handling of the vast amount of data obtained by quantitating the immune response. These concepts are "distance" between antibody responses and "immune response width". The 20 patients included in this study were pollen-allergic patients who underwent specific immunotherapy in a 3-year prospective study. It was found that the immune response during immunotherapy was restricted to IgG1 and IgG4 antibodies. The semi-quantitative CRIE analysis correlated with the RAST analysis for the IgE samples before start of immunotherapy, for the IgG1 samples at week 12, and for all the IgG4 samples. During immunotherapy the number of IgG1 antibodies directed to the different antigens increased towards 11 antigens and decreased towards six. For the IgG4 antibodies the number of reactions increased towards 15 antigens and decreased towards four. The increase is generally paralleled by an increase in quantitative immune response as well. For some of the antigens a rise in the IgE antibodies is contrasted by a fall in the IgG4 antibody response, and for other antigens the opposite was true, indicating a regulatory mechanism between the IgE and the IgG4 synthesis. The IgE immune response to a number of antigens, including the major allergens before the start of immunotherapy, was quantitatively diminished during the period of immunotherapy when IgG1 was present early (week 12) in the period, and for other antigens there was a rise in IgE without an early IgG1 antibody response. This suggests that IgG1 can have a regulating influence on the IgE synthesis. Finally, we have found that IgE antibodies with specificities not present in the samples taken before immunotherapy were formed during immunotherapy. These new IgE antibodies do not, however, seem to impair the outcome of treatment.

Synthesis, isolation, and characterization of conjugates of ovalbumin with monomethoxypolyethylene glycol using cyanuric chloride as the coupling agent

The experimental conditions for the preparation of conjugates of ovalbumin (OA) and monomethoxypolyethylene glycol (mPEG) of a preselected average degree of conjugation, n, using cyanuric chloride as the coupling agent, have been investigated with emphasis on purification and characterization of the products. These conjugates served as prototypes of tolerogenic mPEG derivatives of antigenic proteins which were capable of suppressing in mammals the immunological response to the corresponding unmodified antigens. In other studies in this laboratory, the tolerogenicity of OA(mPEG)n conjugates was found to be a function of n. The reproducibility of the reaction leading to the production of OA(mPEG)n conjugates was shown to depend primarily on the reactivity of the mPEG-cyanuric chloride intermediate, which--for best results--had to be synthesized under completely anhydrous conditions. Isolation of the OA(mPEG)n conjugates was optimized by the use of ion-exchange chromatography whereby rapid removal of large amounts of uncoupled intermediate from the conjugate was achieved; the conditions of fractionation were affected by the degree of conjugation. This method of purification was superior to dialysis, ultrafiltration, and gel filtration. Furthermore, by the application of analytical hydrophobic interaction HPLC it was possible to differentiate among conjugates of different degrees of conjugation and to establish the absence of any detectable free OA in any of the preparations. The quantity of mPEG in the conjugates was determined directly by NMR.

A fluorometric assay of the degree of modification of protein primary amines with polyethylene glycol

An alternative primary amine assay utilizing 4-phenylspiro[furan-2(3H),1'-phthalan]-3,3'-dione (fluorescamine) is compared with the frequently applied trinitrobenzenesulfonic acid assay as a means of estimating protein primary amine modification with cyanuric chloride attachment of polyethylene glycol (PEG). The results of the two assays are compared for three different proteins and several advantages of the fluorescamine assay are emphasized. In particular, the fluorescamine assay was found to be unaffected by free PEG up to 0.08% in the assay mixture. The fluorescamine assay can be used to measure the partition coefficients of native or PEG-modified protein in two-phase aqueous polymer systems.

The subclass nature and clinical significance of the IgG antibody response in patients undergoing allergen-specific immunotherapy

The purpose of this paper is to discuss the methodological difficulties in quantitation of human IgG subclass antibodies to allergens, to describe the subclass nature of the IgG antibody response in patients undergoing allergen-specific immunotherapy, and to discuss the possible immunological functions and clinical significance of allergen-specific IgG antibodies of different subclasses. Based on results obtained by use of assays with documented specificity it is concluded that the IgG antibody response during allergen-specific immunotherapy is IgG1 and IgG4 restricted, although low levels of IgG2 and IgG3 antibodies to some allergens may occur. In most patients the early IgG antibody response is IgG1 dominated and the late IgG4 dominated. A too early or too pronounced IgG4 dominated antibody response seems to indicate a poor clinical outcome of immunotherapy with inhalant allergens, whereas a pronounced early IgG1 antibody production has been found to be associated with a decrease in synthesis of IgE antibodies to an insect venom. It is therefore proposed that an early IgG1 dominated response is necessary to induce suppression of the ongoing IgE antibody production, which in its turn may be a prerequisite for long-lasting clinical effect. The possibility of induction of an early IgG1 dominated response in every patient by use of alternative immunotherapy procedures is discussed.

Effect of polyethyleneglycols (PEG 600 and PEG 6000) and bovine serum albumin on myeloperoxidase-mediated release of [3H]-serotonin from rat peritoneal mast cells in vitro

Rat peritoneal mast cells in vitro released [3H]-serotonin in the presence of halide (I-), myeloperoxidase (MPO), and a H2O2-generating system. The degranulation was partly inhibited with low concentrations of bovine serum albumin (BSA; 0.1-1% w/v), or polyethyleneglycols (PEG 600 or PEG 6000, 0.1% w/v). Furthermore, PEG 600 and PEG 6000 enhanced the stabilization achieved with 0.1% BSA. The results may provide a new aspect on antigenicity of PEG-modified allergens, and on mast-cell response at an inflammatory site.

In vivo effects of ovalbumin-conjugated muramyl peptides on the anti-ovalbumin IgE and IgG responses in mice

The effects of pretreatments of BALB/c mice with several conjugates of MDP and MDP-Lys to ovalbumin before immunization with ovalbumin (OA) were tested on the anti-OA IgE responses. Pretreatment with MDP-Lys-OA, but not with MDP-OA, induced an inhibition of the anti-OA primary and secondary responses, as measured by passive cutaneous anaphylaxis (PCA) and also by mast cell degranulation. The inhibition by pretreatment with MDP-Lys-OA was obtained whether it was administered in Freund's incomplete adjuvant (FIA) or in saline. This IgE suppression was accompanied by an enhancement of IgG2a and IgG2b anti-OA antibodies, with no change in the specific IgG1 levels. Loss of antigenicity of OA, detected by the lack of degranulation of peritoneal mast cells sensitized by IgE anti-OA, was observed in the MDP-Lys-OA but not in the MDP-OA conjugates. This loss of antigenicity appears to correlate with the ability of the conjugate to induce suppression of the specific IgE response.

A new procedure for the synthesis of polyethylene glycol-protein adducts; effects on function, receptor recognition, and clearance of superoxide dismutase, lactoferrin, and alpha 2-macroglobulin

A new, simplified technique for the synthesis of polyethylene glycol (PEG) derivatives of proteins utilizing 1,1'-carbonyldiimidazole for PEG activation, is described. PEG derivatives of superoxide dismutase, alpha 2-macroglobulin, alpha 2-macroglobulin-trypsin, and lactoferrin were prepared and studied. Superoxide dismutase coupled to PEG preserved 95% of its original activity while its plasma half-life increased from 3.5 min to 9 or more hours depending on the PEG derivative studied. PEG-derivatized alpha 2-macroglobulin showed decreased protease binding activity but PEG derivatives of performed alpha 2-macroglobulin-trypsin demonstrated no loss of activity. The plasma clearance of PEG-alpha 2-macroglobulin-trypsin was prolonged significantly compared to native alpha 2-macroglobulin-trypsin, particularly when a high-molecular-weight PEG was coupled to the protease inhibitor complex. The plasma clearance half-life of lactoferrin was increased 5- to 20-fold by this modification. Trinitrobenzenesulfonic acid titration studies demonstrated that epsilon-amino groups of lysine residues are modified by the coupling of carbonyldiimidazole-activated PEG to proteins.

Effect of polyethyleneglycol (PEG) on spontaneous and polymyxin B-induced histamine release from rat peritoneal mast cells

Mast cells were isolated from the peritoneal cavity of rat and purified by centrifugation in a gradient of Percoll. The spontaneous and polymyxin B-induced release of histamine was studied after preincubation of the cells with polyethyleneglycols (PEGs) of different molecular weight (200-20,000 dalton) and with fatty acid derivatives of PEG 6000. It was found that very low concentrations (less than 0.1%) of PEG 6000 reduced the spontaneous and polymyxin B-induced release of histamine to a greater extent than the same concentration of bovine serum albumin. The inhibition increased with the size of the PEGs, but was little affected by the presence of fatty acid ligand bound to PEG.

Allergic hypersensitivity to the herbicide 2,4-D in BALB/c mice

Following several reports of human allergic hypersensitivity, the ability of 2,4-D (2,4-dichlorophenoxyacetic acid) to elicit 2,4-D-specific IgE antibodies and delayed-type hypersensitivity in BALB/c mice was studied. 2,4-D-specific IgE antibodies were detected in mouse sera following the second intraperitoneal immunization with 1, 10, or 100 micrograms 2,4-D-keyhold limpet hemocyanin conjugate with aluminum hydroxide adjuvant. Specific IgE was determined with the rat passive cutaneous anaphylaxis test using a conjugate of 2,4-D with bovine serum albumin for challenge. The highest antibody titers and a measurable response in all mice were seen in the group that received 1 microgram of 2,4-D conjugate. Dinitrophenyl-specific IgE was measured at all intervals examined in mice immunized with a dinitrophenyl-keyhole limpet hemocyanin conjugate. 2,4-D applied epicutaneously on 2 d or over 4 wk failed to elicit delayed-type hypersensitivity as measured by change in ear thickness, incorporation of 5-[125I]iodo-2'-deoxyuridine, or histology following challenge on the ear. No 2,4-D-specific IgE antibodies were detected in serum during the 4-wk sensitization period. Similar treatment with a known sensitizer, dinitrofluorobenzene, produced delayed hypersensitivity. Following 4 wk of dosing, low titers of dinitrophenyl-specific IgE antibodies were elicited.

Suppression of IgE antibodies with conjugates of haptens or allergens and synthetic hydrophilic polymers

A variety of allergens and allergenic haptens can be converted to nonimmunologenic and tolerogenic derivatives by conjugation to nonimmunogenic, hydrophilic, synthetic polymers, such as mPEG, PVA, and PVP. The resulting conjugates of common allergens and of small molecules, such as those responsible for drug allergies, can potentially be used therapeutically for the specific suppression of the IgE antibodies that mediate the corresponding allergic manifestations of the immediate type. All these conjugates exert their immunosuppressive effect in mice by activating suppressor T cells; hapten-PVA and hapten-PVP conjugates--as distinct from antigen-mPEG conjugates--also appear to inactive the hapten-specific B cell population.

Equine immunology 2: immunopharmacology--biochemical basis of hypersensitivity

In general, 4 types of hypersensitivity reactions can be defined according to their immunological basis and clinical appearance. The differing mechanisms of these responses are described with particular reference to chemical mediators which through their pharmacological actions contribute to the clinical manifestations of hypersensitivity. Chemical mediators may exert their influence locally or systemically through their action on effector, tissues or organs and in addition, may be involved in the recruitment of cells of specific type to the site of the reaction. The possible role of these mediators in hypersensitivity in the equine species is discussed to provide a background for a subsequent paper which will be concerned with the therapy of hypersensitivity conditions.

Milk protein immune complexes in the cow and calf

Immune complexes formed between IgG and the milk protein beta-lactoglobulin have detected in bovine colostrum and in the serum of young calves. Complexes were present in all calves studied and the data suggest that they were passively acquired during suckling. The complexes had a molecular weight of 185 000 strongly suggesting the molecular configuration Ab1Ag2. Their half-life in calf serum was 12-21 days. alpha-Lactalbumin was also detected in calf serum and appeared to be complexed in a similar way. Attempts to dissociate the complexes at low pH and by reduction and separation of IgG heavy and light chains led to the release of only a small percentage of complexed beta-lactoglobulin. The results suggest that transient autoimmunity to milk and the transfer of milk protein complexes from mother to young are normal events in cattle. An immunosuppressive role for the immune complexes in postulated.

Suppression of IgE antibodies to the (4-hydroxy-3-iodo-5-nitrophenyl)acetyl (NIP) group and induction of NIP-specific suppressor cells with NIP-poly-N-vinylpyrrolidone conjugates

The capacity of (C57BL/6 x DBA/2)F1 mice to produce anti-(4-hydroxy-3-iodo-5-nitrophenyl)acetyl (NIP) IgE antibodies, as a result of immunization with 1 microgram of NIP2-ovalbumin (OA) in the presence of A1(OH)3, was specifically suppressed by treatment of mice, either before or after immunization, with tolerogenic conjugates consisting of the hapten coupled to poly-N-vinylpyrrolidone (PVP) with an average mol. wt of 10 000. The suppression was hapten-specific, since it did not affect the immune response of the host to OA. The unresponsive state of the spleen cells of mice which had been tolerized with respect to NIP was maintained even after cell transfer into X-irradiated, syngeneic recipients and was shown to be due to hapten-specific suppressor cells. However, the splenic B cells of these mice did not possess any suppressive activity. The generation of an effective number of suppressor cells required between 1 and 2 days following the administration of the tolerogen. The suppressive effects observed on adoptive transfer could not be attributed to the carry-over of the tolerogen, which might have been associated with the spleen cells of the donor mice, since the transfer of B cells of tolerized mice or of mice which had received 2 mg of the tolerogen 2-24 h before cell transfer did not abrogate the capacity of spleen cells of immune mice to mount an anti-NIP response. Hence, it may be concluded that NIP2-PVP induced, in addition to a probable receptor of blockade of B cells, a central inhibitory mechanism which led to the development of an effective number of suppressor cells within 1 to 2 days after administration of NIP2-PVP.

Preparation of protein conjugates with alkoxypolyethylene glycols

Alkoxypolyethylene glycols can be converted to O-alkoxypolyethyleneglycoxy-S-carboxamidomethyldithiocarbonates. These dithiocarbonates are useful for the preparation of protein conjugates with alkoxypolyethylene glycols. Studies with model compounds suggest that sites of reaction are primarily the amino groups of proteins and, to a lesser extent, the aliphatic and phenolic hydroxyl groups. Antigen E, which is an allergenic protein from ragweed pollen, was modified with different alkoxypolyethylene glycols by the above procedure. The size and the hydrophobicity of alkoxypolyethylene glycols used were found to influence the reduction in antigenic activity of conjugates.

Hapten-specific T-cell unresponsiveness induced bybenzylpenicilloyl autologous gamma globulin conjugates in human lymphocyes in vitro

The aim of these studies was to determine whether unresponsiveness to the main determinant of penicillin, benzylpenicilloyl, can be induced in human peripheral lymphocytes in vitro by conjugates of benzylpenicilloyl (BPO) autologous gamma globulin (HGG). Initially it was shown that conjugates of BPO-keyhole limpet hemocyanin (KLH) elicited lymphocyte proliferation in the peripheral blood lymphocytes of six out of nine adult individuals in vitro. In contrast, conjugates of dinitrophenylated KLH and of BPO-HGG and the carriers HGG and KLH alone failed to do so. Similarly, release of the non-specific helper factor, lymphocyte mitogenic factor (LMF) occurred only after BPO-KLH stimulation. LMF activity was measured by B-cell proliferation and incorporation of radioactive amino acids into secreted immunoglobulin. Treatment with BPO-HGG for 24 h in vitro inhibited BPO-KLH-induced lymphocyte proliferation and LMF release. Treatment with either HGG, dinitrophenylated HGG, BPO-KLH, or BPO-human serum albumin failed to abrogate T-cell lymphocyte proliferation of human lymphocytes in vitro. The antigen specificity of the reduced immunologic responsiveness was further demonstrated by the observation that lymphocytes treated with BPO-HGG for 24 h in vitro responded normally to tetanus toxoid antigen.The data suggest that conjugates of BPO-HGG induce hapten-specific helper T-cell unresponsiveness in vitro.