Increased susceptibility of stored erythrocytes to anti-band 3 IgG autoantibody binding

When human blood was stored in a citrate-phosphate-dextrose (CPD) solution at 4 degrees C, the susceptibility of the erythrocytes to binding of autologous IgG increased. The autologous IgG binding was partially inhibited by purified Band 3 glycoprotein and its oligosaccharides. The susceptibility of the erythrocytes to binding of 125I-labeled anti-band 3 IgG autoantibody similarly increased. The results indicate that the anti-band 3 binding sites composed of Band 3 oligosaccharides were generated on the cell surface. The rate of the increase in the susceptibility of the stored cells to the antibody binding was lowered when blood was stored in a CPD solution containing L-ascorbic acid or erythorbic acid, suggesting involvement of an oxidative mechanism in the generation of the binding sites. The cytoplasmic glutathione level of erythrocytes gradually decreased during the blood storage. Storing blood in a CPD solution containing glutathione monoethylester or glutathione monoisopropylester resulted in partial prevention of the decrease in cytoplasmic glutathione level and of the increase in the IgG-binding ability of the cells. Similar preventive effect of glutathione monoethylester was observed in the binding of 125I-labeled anti-band 3 autoantibody to the stored erythrocytes. Thus, the increase in the susceptibility of the stored erythrocytes to anti-band 3 binding may be caused, at least partially, by an oxidative stress resulting in a decreased cytoplasmic glutathione level.

[The mechanisms of the immunotropic effects of organophosphorus compounds]

The effects of acute poisoning with anticholinesterase insecticide dimethyldichlorvinylphosphate (DDVP) in doses 0.25; 0.5 and 1.0 LD 50, immobilisation stress (6-hour), hydrocortisone (100 mg/kg) and acetylcholine--A (5 mg/kg) on the basic immune responses were investigated in experiments on CBA mice. It was shown that increased migration of founder hemopoietic cells from the bone marrow was caused by the effect of A and that of T-cells from the thymus was induced by the actions of corticosterone (CS) and A. Suppressions of delayed-type hypersensitivity reaction, natural and antibody-dependent cellular cytotoxicity humoral immune response were directly associated with concentration of CS in the blood and inhibition of alpha-naphthylbutyratesterase in spleen cells. The function of nonspecific and specific mechanisms in the formation of immunodeficiency after intoxication with organophosphates chemicals was found to differ in immune resections under study.

Solvent effect on testosterone-antitestosterone interaction

The inhibition of the binding between testosterone and antitestosterone antiserum caused by organic solvents was studied at pH 7.4, 298 K. Inhibition curves were obtained at variable ranges of molar fractions for the following solvents: methanol (range 0-0.4), ethanol (0-0.317), 1-propanol (0-0.082), 2-propan-ol (0-0.260), t-butanol (0-0.223), ethylenglycol (0-0.189), 2-methoxyethanol (0.036), 2-butoxyethanol (0-0.063), 1,4-dioxan (0-0.124), tetrahydrofuran (0-0.238) and acetonitrile (0-0.392). Steroid-antibody binding decreases with increasing molar fraction of solvent in the reaction mixture for all but tetrahydrofuran and acetonitrile, which enhance binding at low molar fraction then cause a sharp inhibition. Molar fraction of solvent that causes a 50% binding inhibition is uncorrelated to some solvent properties (i.e. dielectric constant, polarity index, dipole moment) but is inversely correlated to the molecular mass of the solvent. The correlation becomes better by taking into account the length of the solvent molecule, or the Randic molecular connectivity index, suggesting that binding inhibition could be related to the length of the solvent molecules that displace water around the steroid molecule. However, the increase of binding observed at low molar fraction with tetrahydrofuran and acetonitrile, together with very different shapes of inhibition curves suggest that a molecular mechanism based on the differential solvation of the steroid by solvent and water molecules must be taken into account to explain adequately the solvent effect on testosterone-antitestosterone interaction.

Selection of monoclonal antibodies that bind and inhibit tissue-type plasminogen activator

Three monoclonal antibodies raised against tissue-type plasminogen activator (t-PA) were selected for their ability to inhibit solid-phase bound t-PA. Each monoclonal antibody blocked the release of p-nitroaniline from H-D-Ile-Pro-Arg-pNA (S-2288). The first antibody 1D2 was a gamma 2b, kappa with KD = 8 x 10(-9) M, the second antibody 2B9 was a gamma 1, kappa with KD = 2 x 10(-9) M, and the third antibody 5A9 was a gamma 1,kappa with KD = 4 x 10(-10) M. In solution-phase format each antibody blocked the conversion of plasminogen to plasmin as judged by a plasmin assay and also inhibited t-PA-mediated lysis of plasma fibrin clot in plasma. The binding of each 125I-radiolabeled antibody to t-PA was inhibited by any one of the three antibodies, suggesting that they recognized a common epitope on t-PA which was absent on unfolded t-PA. We concluded these antibodies bind near t-PA active site since PPACK treatment lowered binding of two antibodies. We believe solid-phase chromogenic substrate assay may be a useful way to screen for antibodies directed against the active site of proteases.

Heparin and pregnancy in women with a history of repeated miscarriages

Many patients who experience recurrent spontaneous abortions (RSA) have high titered antibodies to trophoblast antigens and/or negatively charged phospholipids. Pregnancy success has been documented in some of these patients subsequent to heparin treatment. The effect of heparin on in vitro assays used to detect antibodies to phospholipids and trophoblast antigens has been investigated. We have found that complement-mediated detection of antibodies to trophoblast and lymphocyte antigens is inhibited by absorption of sera with solid-phase heparin. The data show that such inhibition involves an inhibitor and a heparin-sensitive regulator of the inhibitor. Heparin inhibits binding of antiphospholipid antibodies to phospholipids in solid-phase ELISA. The mechanism for this inhibition appears to involve an interaction between heparin and antibody to phospholipid. These findings reveal novel heparin-mediated reactions that bridge immunological and hematological interactions. The extent of heparin modulation of these antibody reactivities should be clarified in future clinical trials involving heparin treatment for RSA.

Trimucytin: a collagen-like aggregating inducer isolated from Trimeresurus mucrosquamatus snake venom

Trimucytin is a potent platelet aggregation inducer isolated from Trimeresurus mucrosquamatus snake venom. Similar to collagen, trimucytin has a run of (Gly-Pro-X) repeats at the N-terminal amino acids sequence. It induced platelet aggregation, ATP release and thromboxane formation in rabbit platelets in a concentration-dependent manner. The aggregation was not due to released ADP since it was not suppressed by creatine phosphate/creatine phosphokinase. It was not either due to thromboxane A2 formation because indomethacin and BW755C did not have any effect on the aggregation even thromboxane B2 formation was completely abolished by indomethacin. Platelet-activating factor (PAF) was not involved in the aggregation since a PAF antagonist, kadsurenone, did not affect. However, RGD-containing peptide triflavin inhibited the aggregation, but not the release of ATP, of platelets induced by trimucytin. Indomethacin, mepacrine, prostaglandin E1 and tetracaine inhibited the thromboxane B2 formation of platelets caused by collagen and trimucytin. Forskolin and sodium nitroprusside inhibited both platelet aggregation and ATP release, but not the shape change induced by trimucytin. In quin-2 loaded platelets, the rise of intracellular calcium concentration caused by trimucytin was decreased by 12-O-tetradecanoyl phorbol-13 acetate, imipramine, TMB-8 and indomethacin. In the absence of extracellular calcium, both collagen and trimucytin caused no thromboxane B2 formation, but still induced ATP release which was completely blocked by R 59022. Inositol phosphate formation in platelets was markedly enhanced by trimucytin and collagen. MAB1988, an antibody against platelet membrane glycoprotein Ia, inhibited trimucytin- and collagen-induced platelet aggregation and ATP release.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterisation of residues in antibody binding sites by chemical modification of surface-adsorbed protein combined with enzyme immunoassay

Specific functional group modification of an antibody adsorbed to microtitre plates has been used to probe the binding site residues that determine antigen specificity. Chemical modification of adsorbed protein in tandem with enzyme immunoassay (termed CMAP-EIA) consumes only modest amounts of antibody, while allowing a variety of reagents to be rapidly screened in situ. Modification of tyrosine and arginine residues with 1-fluoro-2,4-dinitrobenzene, and p-hydroxyphenylglyoxal resulted in reduced binding of polysaccharide antigen from Yersinia enterocolitica O-polysaccharide to its homologous monoclonal antibody, YsT9-1. Modification with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide under various conditions indicated that carboxylate groups may also be involved. Parallel experiments with diethylpyrocarbonate and acetic anhydride were used to rule out the involvement of histidine and lysine residues respectively. In all cases, binding of an anti-idiotypic antibody, AJ5, could only be reduced at concentrations of modifying reagent substantially higher than those required to reduce polysaccharide antigen binding to YsT9-1. The results are discussed with regard to the structure of the combining site of YsT9-1 as determined by X ray crystallography and by modelling, and the role of particular residues in complex formation with antigen and in the idiotope.

[Inhibitory effects of Reitakutuukitokasin'i on the antigen-antibody reaction in rats investigated by measuring the increase in blood histamine level and the histamine release from peritoneal mast cells]

The antiallergic effects of Reitakutuukitokasin'i (RKS) on the increase in blood histamine level by antigen challenge were investigated in actively sensitized rats in comparison with those of azelastine and disodium cromoglycate (DSCG). The increase in blood histamine level after a systemic anaphylactic reaction elicited by intravenously injected antigen (egg albumin) was significantly inhibited by oral and intravenous administrations of RKS and azelastine or DSCG. Namely, RKS at 50 and 100 mg/kg (p.o.) caused 17% and 28% inhibition, respectively, and azelastine at 5 and 10 mg/kg (p.o.) caused 28% and 29% inhibition, respectively. RKS at 0.1 and 0.5 mg/kg (i.v.) caused 33% and 29% inhibition, respectively, and DSCG at 10 mg/kg (i.v.) caused 53% inhibition. However, large doses of RKS (500 mg/kg, p.o., 2.5 and 10 mg/kg, i.v.) caused no significant inhibition. The histamine release from rat peritoneal mast cells (RPMC) by antigen-antibody reaction was also investigated, and proved to be inhibited significantly by RKS. Namely, RKS at 5 x 10(-4), 10(-3) and 2 x 10(-3) g/ml caused 42, 71 and 79% inhibition, respectively. These results suggest that RKS is an antiallergic drug similar to azelastine and DSCG with a common inhibitory action on the release of histamine.

[The peptide modulation of immune reactions]

A dose-dependent immunomodulating effect of synthetic low-molecular weight peptides was found in CBA mice. Talcin and its analogue, rigin, tripeptide SKE, substance P and its analogue, and vasopressin were shown to produce an immunostimulating effect, whereas vasopressin tetrapeptide, arginyl-asparagine, and tripeptide SKD showed an immunosuppressive effect. The immunomodulatory effect of the peptides tested was associated with the presence of amino acids such as arginine, lysine, tyrosine, glutamic acid in their chemical structure. These amino acids are essential in the mechanisms of immune responses.

[The effect of synthetic beta-carotene on the primary immune response of CBA strain mice]

Synthetic beta-carotene was studied for its effect on a primary humoral immune response to thymus-dependent antigen of sheep red cells. beta-Carotene was demonstrated to have immunomodulatory action. The effect depended on the dose of the agent and its administration time after immunization. The agent could produce both stimulant and suppressive effects.

CD4 changes conformation upon ligand binding

Aurintricarboxylic acid (ATA) has been shown to block the binding site for both HIV gp120 and mAb anti-Leu 3a on CD4. We have unexpectedly found that brief treatment with > or = 1 micrograms/ml ATA rapidly disengages another mAb, OKT4E, after it has been bound to CD4 on human PBL. OKT4E is specific for a discontinuous epitope overlapping the MHC class II-binding region in the N-terminal CD4 domain. Interestingly, among 10 other mAb tested, only anti-Leu 8, specific for a leukocyte homing receptor is also quickly released from the cells by ATA treatment. Disengagement of the OKT4E mAb is also seen on a CD4-positive cell line (HPB-ALL) and with recombinant soluble CD4 (sCD4) bound to immobilized OKT4E. In all of these cases, disengagement is prevented if OKT4E is cross-linked, or the Leu 3a site is blocked by the mAb, but not by gp120. Photobleaching fluorescence resonance energy transfer (pFRET) measurements suggest that OKT4E is released as an indirect consequence of ATA-evoked conformational changes of CD4. Similar changes were detected as a result of gp120 binding to PBL. These data raise the possibility of a novel type of immunomodulation: induced disengagement of a bound ligand from its Ag.

Galactose to ceramide linkage is essential for the binding of a polyclonal antibody to galactosyl ceramide

Characterization of a polyclonal antibody to galactosyl ceramide (Gal-Cer) which inhibits the internalization and infection of HIV-1 in neural cell lines was carried out. Polyclonal antibody to Gal-Cer was produced by injecting rabbits with Gal-Cer liposomes. The specificity of anti-Gal-Cer binding was studied by high performance thin layer chromatography (HPTLC)-based immunoassay. Using natural and semisynthetic lipids, the specificity of anti-Gal-Cer interaction was studied. The antibody bound to Gal-Cer and its derivatives. The antibody did not bind to glucosyl ceramide or lactosyl ceramide. Glucosyl ceramide differs from Gal-Cer by a hydroxyl group at the fourth carbon and in lactosyl ceramide galactose is linked to ceramide by an intervening glucose molecule. This indicates that D-galactose linked to ceramide is essential for binding. Removal of fatty acid from Gal-Cer, as seen with N-palmitoyl- and N-oleoyl Gal-Cer, had no effect on the binding. It appears that the third carbon of Gal-Cer is not involved in the binding. This is supported by the binding of anti-Gal-Cer to sulfatide or GM4 in which sulfate or sialic acid are added at the third carbon of Gal-Cer, respectively.

Absence of a specific effect of free radicals on HLA-B27

The spondylitis associated HLA-B27 epitope includes a characteristic unpaired cysteine at amino acid position 67. On some B27 molecules the thiol (-SH) side chain of this residue seems to be available for chemical interactions. The possibility that free radicals produced during inflammation might specifically affect this group was investigated in this work. Cells bearing HLA-B27 were exposed to free radicals generated by ultraviolet irradiation or hydrogen peroxide, and HLA antigens were then measured by flow cytometry. Binding of monoclonal antibodies to B27 was not affected. These results do not support a specific susceptibility of HLA-B27 to damage by free radicals, despite its apparently vulnerable structure.

[The status of and causes of change in the immunological reactivity of patients with iron-deficiency anemia]

The role of the immunity system in the pathogenesis of iron deficiency anemia and its complications was studied in 200 patients and in the experiment on 55 non-inbred white rats. The state of nonspecific resistance, humoral and cellular components of immunity was investigated. It has been shown that iron deficiency leads to imbalance in the immunity system. The degree of the affection and disorders in the integration between separate parameters of the immunity system determine the possibility of complications and influence the course of concomitant diseases. Ferrotherapy produces a positive effect on the immune status of patients with iron deficiency anemia.

Use of a zwitterionic detergent for the restoration of the antibody binding capacity of immunoblotted Francisella tularensis lipopolysaccharide

A method for the partial restoration of the antibody binding capacity of Francisella tularensis lipopolysaccharide (LPS) following denaturation (dissociation) in boiling sodium dodecyl sulfate (SDS) is described. The method relies on the presence of a zwitterionic detergent in the matrix of an SDS-polyacrylamide gel and in the transfer buffer during an immunoblot. F. tularensis LPS, which had lost its earlier capacity to bind to a particular monoclonal antibody in the normal blot procedure, did bind following the addition of the zwitterionic detergent to the polyacrylamide gel and transfer buffer. A number of detergents were tested but most success in restoring antibody binding was achieved with Zwittergent 3-08. This simple modification to the immunoblot procedure proved helpful in identifying a monoclonal antibody specific to hot phenol-extracted F. tularensis LPS.

Protective effect of 16,16-dimethyl prostaglandin E2 on isolated rat hepatocytes against complement-mediated immune attack

16,16-Dimethyl prostaglandin E2 was examined for its ability to inhibit complement-mediated in vitro hepatocytolysis by an antigen-antibody reaction. In the presence of fresh rat serum as a source of complement, 5-min culture of isolated rat hepatocytes with a monoclonal antibody against a rat liver-specific membranous antigen resulted in a marked, significant elevation in lactate dehydrogenase leakage into the culture medium. However, with heat-inactivated rat serum, such a reaction did not occur, indicating that the hepatocytolysis induced by the antibody was attributable to the membrane damaging action of complement activated by an antigen-antibody reaction. Pretreatment of the hepatocyte with 16,16-dimethyl prostaglandin E2 significantly suppressed the cytolytic reaction induced by the antibody in a concentration-dependent manner. These results show that 16,16-dimethyl prostaglandin E2 is capable of protecting isolated rat hepatocytes against the membrane-damaging insult of activated complement.

Calcium-dependent and calcium-independent signals in the conglutinin-binding assay (KgBa) for immune complexes. Influence of anti-collagen-antibodies

A solid phase ELISA conglutinin-binding assay (KgBa) was evaluated for the detection of circulating immune complexes. ELISA wells were coated with purified bovine conglutinin and incubated with test sera. Bound IgG was detected with enzyme labelled anti-immunoglobulin. Heat aggregated IgG which had been "solubilized" (i.e., complement treated by incubation with serum) was employed as a reference. The binding of the complement-reacted IgG to solid phase conglutinin was found to be calcium-dependent and inhibitable with N-acetyl-D-glucosamine (GlcNAc). Prolonged incubation (4 days) of aggregated IgG with serum at 37 degrees C abolished the binding to conglutinin, a finding consistent with the complete degradation of deposited C3b to C3c and C3d. The solubilized IgG that bound to solid phase conglutinin was found by gel chromatography to be of high molecular weight (greater than 600 kDa). Binding of IgG to solid phase bovine conglutinin was also observed to a variable degree in normal and pathological sera. However, in this situation the IgG binding was largely calcium-independent, was not inhibited by GlcNAc and did not decrease after prolonged incubation of the serum at 37 degrees C. The reactive IgG eluted on gel chromatography at the position of monomeric IgG suggesting binding via the antigen binding sites. Binding of this IgG was inhibited by both collagen type II and purified conglutinin. These observations suggest that the assay detects cross-reacting autoantibodies against collagen epitopes, or, alternatively, antibodies against the dietary antigen, bovine conglutinin.

The effect of glycosylation trimming enzyme inhibitors on monoclonal antibody recognition of alpha-sialoglycoprotein epitopes

The human erythrocyte membrane contains four sialoglycoproteins, denoted alpha, beta, gamma and delta (also known as glycophorins A, C, D and B respectively), of which alpha-sialoglycoprotein (alpha-SGP) is the most predominant species. The extracellular portion of alpha-SGP is heavily glycosylated with approximately 15 O-linked carbohydrate side-chains and a single N-linked group. We have used inhibitors of carbohydrate trimming enzymes to investigate the contribution of this single N-glycan moiety towards the recognition of a range of antibody binding sites on alpha-SGP. Two erythromyeloid cell lines, K562 and HEL, were cultured in the presence of these inhibitors and altered binding of antibodies to epitopes adjacent to the N-glycan was observed. Digoxigenin-coupled lectins were used to stain cytocentrifuge preparations and Western blots of cell lysates in order to confirm that modification of N-linked carbohydrate side-chains had been achieved. We suggest that the N-glycan side chain of alpha-SGP has a role in conferring conformational stability upon epitopes which lie in its vicinity.

[The effect of the lipid emulsions used in parenteral nutrition on the immune response capacity]

The preservation or improvement of the immune response capacity in patients on TPN is a priority objective, since in this type of patient, immune deficiencies caused by the main illness, malnutrition or the therapy applied are constant and reflected in the great incidence of septic complications. The use of lipid emulsions in TPN has an obvious clinical repercussion in this respect, due to the intake of EFA (eicosanoid precursors) and the possible negative effect suggested in some studies on the reticulo-endothelium system and other immune functions. This review analyzes the effect of lipid emulsions used in TPN on the immune system. For this purpose, studies on the effect of MCT/LCT an LCT emulsions on the phagocytic and chemotactic functions have been evaluated; antigenic presentation; synthesis of Igs and complement fractions; cellular differentiation and activation; helper or suppressing functions, etc. From the studies reviewed, it can be deduced that there is no clinical evidence of a negative effect caused by lipids when administered in the recommended dosage, whereas an improvement is noted in the immune response capacity, on reverting the nutrition. From comparative studies aimed at evaluating the effect of LCT and MCT/LCT on the different components of the immune system, favourable results have been achieved using the MCT/LCT emulsion, although it is early to say that this will lead to significant clinical repercussions.

Antibodies to carbonic anhydrase in systemic lupus erythematosus and other rheumatic diseases

OBJECTIVE

Autoantibodies to CA were demonstrated in the sera of patients with systemic lupus erythematosus (SLE) and some other rheumatic diseases. This study was undertaken to define the isoform and species specificity of these reactions, as well as to develop a method for detecting immune complexes.

METHODS

Antibodies to CA were sought by enzyme-linked immunosorbent assay (ELISA) and by Western immunoblotting.

RESULTS

An increased prevalence of CA autoantibodies was detected, by both methods, in patients with SLE, scleroderma, and polymyositis, compared with controls. In SLE patients, CA autoantibodies occurred preferentially in those with anti-U1 RNP or anti-U1 RNP and Ro/SS-A. Some sera reacted with only the CA I or CA II isoform, while approximately 50% of sera that were CA positive reacted with both isoforms. The autoantibodies reacted preferentially with the human enzymes, rather than the bovine CA, both on Western blot and by ELISA: Selected IgG F(ab')2 fragments from anti-CA-containing sera specifically inhibited the enzyme activity of CA, and the CA inhibitor acetazolamide partially inhibited the binding of anti-CA to CA. Thus, at least a part of autoanti-CA is directed toward the active site of CA. Finally, CA molecules were detected as immune complexes in sera from selected anti-CA-positive patients.

CONCLUSION

Autoantibodies to CA represent a previously unrecognized autoantibody to an abundant intracellular protein of the human erythrocyte.

Captopril-enhanced binding of PlA1 (HPA-1a) antibodies in posttransfusion purpura

A case of posttransfusion purpura is reported in a 90-year-old patient whose PlA1 antibody (anti-HPA-1a) was found to bind better to HPA-1a in the presence of captopril, a drug the patient had taken. Initially, IgG antibodies were found in the serum that reacted with normal platelets, but the binding of the antibody was increased in vitro by captopril, which suggested that captopril was responsible for the thrombocytopenia. However, in vitro studies demonstrated that the patient's platelets were negative for HPA-1a and that anti-HPA-1a was present in the serum, both of which findings were consistent with the diagnosis of posttransfusion purpura. The binding of this antibody was enhanced 50 percent by captopril in vitro, and increased binding in the presence of captopril did not occur when the anti-HPA-1a was removed. Similar results were obtained with serum containing anti-HPA-1a from another patient with posttransfusion purpura. Thus, captopril may increase the binding of anti-HPA-1a and confuse the determination of the cause of acute thrombocytopenia.

[The possible reasons for an increase in the concentration of middle-weight molecules in pathology]

Human plasma and blood were treated by kaolin, thromboplastin, streptokinase, phytohemagglutinin, hydrogen peroxide, and Fe2+. An increase in the amount of median-mass substances was found after incubation. The obtained data showed that activation of limited proteolysis, immunity, and peroxidation could be the cause of increase of median-mass substances in pathological conditions.

Comparison of clinical and experimental data from an animal model of pulmonary immunologic sensitivity

Isocyanates are highly reactive chemicals capable of causing a multitude of toxicologic effects including respiratory irritation, dermal irritation, contact sensitivity, and pulmonary hypersensitivity. In order to probe the mechanism(s) underlying these reactions, an animal model has been developed. The guinea pig model reproduces both the respiratory and immunologic effects of isocyanates that have been observed clinically. In experimental animals and in humans, isocyanates induce immunologic reactions with specific antibody formation, including IgE. This finding allows development of diagnostic reagents to assess isocyanate sensitivity. Further characterization of immunologic components in the model is expected to increase understanding of the mechanisms of this immunotoxic disease and develop strategies for treatment and prevention.