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Biomedical subjects

S Avrameas

Publications and source records attributed to S Avrameas.

At least 19 recordsLinked to original sources
PubMed1995

Inhibition of in vitro HIV infection by trinitrophenyl-protein conjugates.

Levels of natural antibodies (NAb) with high anti-trinitrophenyl (TNP) activity are increased during human immunodeficiency virus (HIV) infection. The aim of the present study was to examine the anti-HIV effect of natural anti-TNP antibodies, as well as that of their internal image, TNP antigen, on HIV infection in vitro. The results obtained with anti-TNP antibodies, as assessed by syncytia formation, were variable, although they demonstrated an inhibitory effect. In contrast, using RT activity assay plus evaluation of syncytia formation and the viral cytopathic effect, we found that bovine serum albumin (BSA) bearing different TNP groups was able to inhibit HIV infection of peripheral mononuclear cells and T4 cell lines without affecting cell metabolism or proliferation. BSA alone was devoid of activity; the antiviral effect depended on TNP substitution of the BSA molecule, and passage through an anti-TNP immunoadsorbent abolished this effect. The mechanism by which TNP exerts this antiviral effect is unclear. Antigenic epitopes may be shared by HIV and TNP, since monoclonal antibodies directed against various HIV proteins reacted with TNP in an enzyme immunoassay. TNP-BSA, however, did not bind to the CD4 receptor.

Animals↗
PubMed1995

Defects in the regulation of anti-DNA antibody production in aged lupus-prone (NZB x NZW)F1 mice: analysis of T-cell lymphokine synthesis.

(NZB x NZW)F1 (B/W) mice spontaneously develop a lupus-like syndrome characterized by an increased level of autoantibodies in old mice. We analysed the role of T cells in the regulation of anti-DNA antibody production by B cells in vitro as a function of age. In cultures of old mouse T and B cells, IgG and IgM anti-DNA antibodies were synthesized at high levels, in contrast to consistently lower amounts, particularly of IgG, measured in cultures of young mouse cells. Addition of young mouse T cells to old B cells inhibited IgG, but not IgM, anti-DNA production, whereas T cells from old mice stimulated IgG synthesis by young mouse B cells. Addition of supernatants harvested from concanavalin A (Con A)-stimulated T cells to B-cell cultures induced similar effects. Therefore, we evaluated possible modifications of lymphokine synthesis compared to that of the healthy NZW parent. T cells from old mice were able to secrete normal levels of interferon-gamma (IFN-gamma) and interleukin (IL)-10; however, secretion of IL-2 and IL-4 was dramatically decreased. Semi-quantitative polymerase chain reaction analysis of constitutive RNA messengers showed increased IFN-gamma levels in young and old B/W mice, and normal IL-10 mRNA levels in young and higher levels in old mice. Constitutive IL-2 and IL-4 mRNA were detected only after Con A stimulation and their levels decreased in old compared to young B/W mice; in particular IL-2 mRNA was considerably lower in old B/W than in control NZW mice. Taken together, these results suggest that, despite constitutive T-cell abnormalities, young B/W mice are able partially to control their lymphokine production, whereas aged mice exhibit a deficient synthesis, associated with an increased capacity to produce IFN-gamma.

Aging↗
PubMed1994

[Physiological autoimmunity].

The serum of normal individuals contains antibodies directed against their own antigens (autoantigens). These autoantibodies are the main and the best known component of normal autoimmunity. They mostly involve polyreactive (one antibody recognising several antigens) IgM, but also IgG, usually having low affinity for antigens. The role of natural autoimmunity is becoming better understood. It participates in the equilibrium of the immune system, contributing to controlled production of antibodies, accelerated elimination of external antigens or aged autoantigens, and to triggering of a specific immune response. Some data suggest that the action of autoantibodies in homeostasis can extend beyond the immune system. Many pathological states, of immune nature or not, are associated with an increase or diminution of the titre of natural autoantibodies. The mechanisms and consequences of these changes remain to be elucidated.

Animals↗
PubMed1994

Beneficial effect of polyclonal immunoglobulins from malaria-infected BALB/c mice on the lupus-like syndrome of (NZB x NZW)F1 mice.

We previously reported that infection of BALB/c mice with the parasite Plasmodium chabaudi induces high production of natural autoantibodies. Here we demonstrate that such an infection of lupus-prone (NZB x NZW)F1 (B/W) mice retards the development of their autoimmune disease. Survival and disease hallmarks (high-grade proteinuria and IgG anti-DNA antibodies) were delayed for 6 months when parasite inoculation was given at either 3 or 7 months of age, i.e. before or after the onset of the clinical symptoms. Similar beneficial effects, although less pronounced, were obtained when mice were treated with a total of 800 micrograms of IgG (P-IgG) or IgM (P-IgM) or 300 micrograms of cryoglobulin preparations isolated from P. chabaudi-infected BALB/c mice while similarly prepared fractions from uninfected mice had little effect. Compared to these fractions, P-IgG and P-IgM contained higher levels of natural antibodies bearing the D23 idiotype characteristic of polyreactive natural autoantibodies with enhanced activity against Fab and Fc fragments of IgG. In surviving mice, the level of anti-DNA antibodies, particularly those of IgG1 isotype, were significantly decreased. Flow cytometric analysis of various T cell subsets showed that the number of cells expressing gamma delta T cell receptor (TcR) antigens which did not vary with age was not modified after P-IgG or P-IgM treatment. In contrast, the number of T cells expressing V beta 8.1,2,V beta 10 and V beta 14 TcR antigens, which increased with age, were significantly reduced. Taken together, these results indicate that parasite infection of mice induces the synthesis of populations of IgM and IgG natural autoantibodies with immunoregulatory properties and that these antibodies attempt, at least transitorily, to rescue a natural autoantibody network that is deficient in B/W mice.

Animals↗
PubMed1994

Natural autoantibodies are involved in the haemolytic anaemia of NZB mice.

NZB is a mouse strain that spontaneously develops autoimmune haemolytic anaemia at 10-12 months of age. We analysed the autoantibodies present throughout their life and compared them to natural autoantibodies found in the normal mouse. Sera and Coombs' antibodies eluted from red blood cells (RBC) were tested for their activities against RBC and a panel of antigens: actin, myoglobin, myosin, tubulin, spectrin, DNA and trinitrophenyl bovine serum albumin (TNP-BSA), F(ab')2 and Fc fragments of IgG by using enzyme immunoassays (EIA) and Western blotting analysis of RBC membrane extracts. In NZB mouse sera, activities of IgM and IgG against the whole panel, compared to those of sera from age-matched BALB/c mice, increased progressively throughout life with oscillating values in parallel with the anti-RBC activity. Two periods of autoantibody production seem to exist: the first is characterized by a fluctuating high level of IgM and stable level of IgG natural autoantibodies, and the second by a rise of IgG natural autoantibodies in parallel with IgG anti-RBC antibodies. The presence of idiotype D23 (IdD23), which is characteristic of natural polyspecific autoantibodies, was high on serum IgM and low on IgG autoantibodies throughout life. To further analyse autoantibody level oscillations, we tested IgM and IgG fractions after their separation from whole serum and observed highly enhanced autoantibody activities of both IgM and IgG. These autoreactivities markedly diminished when the separated IgM and IgG fractions were recombined, suggesting humoral control of the autoreactivity as we had already noted for IgG in normal animals. During the first period of autoantibody production, IgM and IgG antibodies eluted from RBC (Combs' antibodies) and those eluted from serum using an RBC-immunoadsorbent (circulating antibodies) reacted with all RBC membrane components, with all antigens of the panel and with F(ab')2 and Fc. Some of these reactivities were comparable to those exhibited by a monoclonal antibody recognizing bromelain-treated RBC. In the second period, both IgM and IgG Coombs' antibodies reacted more strongly with spectrin, and exhibited new specificities, for example against the band 3 polypeptide. IdD23 was abundant on Combs' IgG antibodies in the second period. Taken together, these data suggest that IgM and IgG natural autoantibodies, able to recognize not only RBC antigens but also other antigens, particularly F(ab')2 and Fc fragment of IgG, predominate in Coomb's antibody population.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1994

Reactivity and structure of a mouse anti-F(ab')2 IgM. Comparison of its variable region sequences with those of a structurally close polyreactive natural IgM.

IE12 is a monoclonal IgM with strong anti-F(ab')2 activity that inhibits the binding of normal mouse IgG to self antigens. In this study, we found that this IgM was also reactive with several monoclonal antibodies (mAbs), myeloma proteins and B lymphocytes from normal BALB/c mouse. The nucleotide sequences of the variable region of the heavy and light chains of IE12 were determined, and compared to those of another mAb already described in the literature. This mAb uses the same light chain and also the same VH, D and JH segments, but unlike IE12, is polyreactive. The comparison of the amino acid composition of these two mAbs and of the computer predictions for their structure and hydrophilicity indicated that the most striking difference between them was located in the third complementarity determining region (CDR3) of the heavy chain. Indeed, they used the same D segment but translated in two different reading frames, leading to different amino acid compositions. The CDR3 of IE12 contains aliphatic amino acids, while that of the polyreactive IgM does not. In addition, IE12 has two prolines, one at each at each extremity of its D segment, that could confer a certain rigidity to this region. Finally, the CDR3 of IE12 is predicted to be hydrophobic, while the one of the polyreactive IgM is predicted to be hydrophilic and more flexible, suggesting that the hydrophilicity and the flexibility of this region might be critical for polyreactivity.

Amino Acid Sequence↗
PubMed1994

Effects of pH or ionic strength on the reactivities of mono- and polyspecific IgG antibodies.

The reactivities of mono- and polyspecific mouse monoclonal antibodies (mAb) were compared by ELISA using immobilized antigens under different conditions, varying the pH or the NaCl concentration. The monospecific group was composed of 6 IgG directed against Staphylococcus aureus capsular polysaccharides and of 3 IgG specific to actin, myosin or tubulin. These antibodies were compared with 6 polyreactive mAb also of the IgG isotype. Marked differences were noted between the reactivities of the mono- and polyreactive IgG. pH variations had little or no effect on the reactivity of monospecific mAb to polysaccharides or to proteins. In contrast, the binding of polyreactive mAb was dependent on the pH, and the profile differed for each antigen. The NaCl concentration had opposite effects on mono- and polyreactive mAb: the binding of almost all the monoreactive mAb was increased at high NaCl concentration, while it was decreased for polyreactive mAb. In contrast, the effects of varying the pH or ionic strength on the coated antigens were negligible. The variation coefficients calculated for the pH and NaCl concentration were higher for the polyreactive mAb under study, which seems to indicate that electrostatic interactions and charged residues might be more important for these mAb than for the monoreactive ones. This characteristic might be one explanation for the particular properties of these polyreactive antibodies.

Animals↗
PubMed1994

Prognostic significance of autoantibodies to laminin in the sera of breast cancer patients: a preliminary report.

Interactions between cancer cells and laminin play an important role in the metastatic cascade. The aim of this retrospective study was to evaluate the presence and the prognostic significance of autoantibodies to laminin in sera of patients with breast cancer. Our study population consisted of 71 high-risk primary breast cancer patients (median follow-up, 6 years). IgG, IgA and IgM were analysed at the time of surgery and before any treatment was given. Concentrations were measured by enzyme immunoassay with a highly purified antigen. IgG, IgA and IgM anti-laminin median values were, respectively 117%, 130% and 97% of normal absorbance. Higher concentrations of IgM to laminin were found in pre-menopausal patients as compared with post-menopausal patients (p < 0.001). Patients with high concentrations of IgG to laminin had lower disease-free (p = 0.003) and overall survival rates (p = 0.003). In breast cancer, assay of IgG to laminin could thus provide a cheap and easy prognostic index available for all patients.

Adult↗
PubMed1994

Characteristics of polyreactive and monospecific IgG anti-laminin autoantibodies in the rat mercury model.

Brown-Norway (BN) rats injected with HgCl2 produce anti-laminin antibodies responsible for an autoimmune glomerulonephritis. The properties of three IgG1 monoclonal antibodies (mAb) previously obtained in this model, and of immunoglobulins eluted from kidneys of diseased rats, were compared in the present study. Two mAb (Hg15 and Hg16) recognized laminin only, while the third one (Hg17) was polyreactive, as were some of the kidney-eluted immunoglobulins; they reacted with laminin and with several other antigens including 2,4,6-trinitrophenyl (TNP). The Hg17 mAb and kidney-eluted polyreactive antibodies were affinity purified using a TNP-bovine serum albumin (BSA) column; their affinity for TNP was high (2 x 10(-8)M, and 1 x 10(-8)M, respectively) but less than that of a TNP-specific (LO-DNP-2) mAb (2 x 10(-11) M). The Hg17 mAb and kidney-eluted antibodies reacted more effectively with TNP28-BSA than with TNP8.5-BSA, while the TNP-specific mAb reacted equally well with both conjugates. The Hg17 mAb was the most cationic (pI: 7) of the anti-laminin mAb and this was even more evident when F(ab')2 fragments were studied (pI: 8.2). The polyreactive kidney-eluted immunoglobulins that bound TNP were also more cationic (pI: 7.4-9.3) than the fraction that did not recognize TNP (pI: 5.8-8.6). The anti-laminin mAb bound in vivo to the glomerular basement membrane, but only the Hg17 mAb could be eluted with DNP alone. This study shows that polyreactive anti-laminin antibodies are produced during this autoimmune disease, and indicates that they may have pathogenic potential.

Animals↗
PubMed1993

Production of highly specific monoclonal antibodies to monensin and development of a microELISA to detect this antibiotic.

Monensin, a polyether antibiotic of molecular weight 671 Da, was converted into a hemisuccinate and covalently linked to bovine serum albumin via the mixed anhydride method. Using this immunogen, polyclonal anti-monensin antibodies were raised in rabbits and monoclonal antibodies were prepared from mice. The specificity of the anti-monensin antibodies was examined by using several structural analogues as the immunogen and by performing direct binding and competitive microELISA assays on Terasaki plates. Rabbit polyclonal antibodies had a dissociation constant (KD) of 5.5 x 10(-8) M for monensin and reacted with nigericin, an antibiotic structurally related to monensin. In contrast, a mouse monoclonal antibody, 2H8, reacted only with monensin and had a much lower KD = 3 x 10(-8) M for monensin. Monoclonal antibody 2H8 was used to develop a competitive microELISA able to detect as little as 5 ng/ml of monensin in solution which corresponds to 75 pg or 110 fmol of this hapten per Terasaki well.

Animals↗
PubMed1993

Autoantibodies in the sera of Trypanosoma cruzi-infected individuals with or without clinical Chagas disease.

Variations in the levels and the specificities of autoantibodies directed against a panel of antigens (cytoskeleton proteins, DNA, laminin) were analyzed in the sera from two groups of humans infected with Trypanosoma cruzi. One group was constituted of apparently healthy blood donors (BD) and the other of patients with clinically confirmed Chagas disease (CCH). In both infected groups, a high proportion but not all sera exhibited dramatic enhancement of IgM and IgG autoantibodies directed against all antigens tested. Sera positive for IgG autoantibodies were generally found more frequently in the CCH than in the BD group, except for anti-actin antibodies more often present in BD sera. Anti-laminin IgG antibodies were present in a similar number of individuals in both groups. Although the titers of anti-laminin IgG antibodies were in general higher in CCH, their dissociation constants were in the same range (7 x 10(-8) - 10(-7) M) in both groups. IgG autoantibodies were demonstrated to be polyreactive with laminin and other self antigens as well. Circulating immune complexes were present in sera from both groups and the activity of the antibodies dissociated from these complexes was directed against all the antigens of the panel. Although the IgE concentration was significantly enhanced in several subjects from both groups, the incidence of positive sera was higher in the CCH (60%) than in the BD (39%) group. Our results demonstrate that autoantibodies with the characteristics of natural autoantibodies are found in both T. cruzi-infected apparently healthy individuals and patients.

Antibody Affinity↗
PubMed1993

Monoclonal IgG and IgM autoantibodies obtained after polyclonal activation, show reactivities similar to those of polyclonal natural autoantibodies.

In this study, we described the properties of two groups of polyreactive IgG monoclonal antibodies (mAb) derived from splenocytes of a Plasmodium chabaudi-infected BALB/c mouse. These IgG mAb reacted with self antigens, but not with the parasite. Depending upon the antigen under study, they showed low (10(-5) M) to high (10(-8) M) affinities. When examined by immunoblotting using mouse organ extracts as the antigen source, each IgG mAb had a different reactivity profile. The IgG2b, but not the IgG2a mAb group, reacted with F(ab')2 fragments of IgG from normal mouse sera, as well as with F(ab')2 fragments of other mAb from the same fusion. Their anti-F(ab')2 activity was inhibited by various antigens, suggesting that the binding sites for these antigens and F(ab')2 fragments were close or overlapping. We also characterized two monoclonal IgM that were strongly and almost exclusively reactive with polyclonal F(ab')2 fragments of normal IgG, and that inhibited the binding of normal polyclonal IgG to self antigens. We previously described such properties for polyclonal IgM from normal mouse sera. The binding of the F(ab')2-reactive IgG mAb to self antigens was also inhibited by normal polyclonal IgM. These results indicate that the IgG and IgM obtained after polyclonal stimulation, exhibit characteristics similar to those of autoantibodies present in normal mouse sera. Furthermore, they confirm our previous studies showing the polyreactivity of polyclonal IgG. Finally, they also show that such IgG mAb exhibit properties similar to those of natural IgM, namely polyreactivity, affinity and connectivity.

Animals↗
PubMed1993

IgG auto- and polyreactivities of normal human sera.

Using a panel of self antigens, IgM autoreactivities were clearly and constantly detected by enzyme immunoassay (EIA) in the sera of 29 normal human individuals. Similarly, IgM autoreactivities in sera were reproducibly detected by immunoblotting, using human organ extracts as the antigen sources. In contrast, IgG reactivities were low in whole sera but were considerably increased after affinity-chromatography purification on protein G-Sepharose. These increases differed from one individual IgG preparation to another and from one antigen to another (from 1-94 times) resulting in a unique IgG autoreactivity pattern for each subject. IgG reactivities diminished markedly when the IgG-depleted serum was added to the isolated autologous IgG. IgM antibodies isolated from sera on F(ab')2 IgG immunoadsorbent partially inhibited the binding of IgG to tubulin and myosin but not to actin. The individual IgG preparations examined separately exhibited, with all the autoantigens of the panel, higher autoreactivities than those of the same-but-pooled IgGs, which in turn were higher than those of a commercially available human IgG preparation obtained from approximately 8,000 healthy donors and used for intravenous injection. Depending upon the individual IgG sample, 31-65% of the IgG were bound to a DNP-Sepharose column and were eluted with DNP-glycine. The isolated anti-DNP antibodies were found to be polyreactive and possess higher autoreactivities than the original IgG preparation for all the antigens of the panel. Similarly, IgG antibodies analysed using an antibody exchange procedure were found to be essentially polyreactive but some apparently monospecific antibodies were also noted. These results suggest that the great majority of IgG present in normal humans are composed of polyreactive autoantibodies. IgG autoreactivities are only marginally expressed in these whole sera because of IgM-IgG, IgG-IgG and other, still unidentified, interactions.

Actins↗
PubMed1993

Common idiotypes expressed on human, monoclonal, abnormal immunoglobulins and cryoglobulins with polyreactive autoantibody activities.

Several human monoclonal immunoglobulins with the same autoantibody activity have been shown to have cross-reactive idiotypes (CRI). In this study, using polyclonal anti-idiotypic antibodies, we found that 28% of human monoclonal immunoglobulins with polyreactive autoantibody activity from myeloma, Waldenström's macroglobulinaemia and cryoglobulinaemia patients shared common idiotype(s). Furthermore, the latter were expressed on human and murine natural MoAbs (respectively in 12% and 22% of the clones tested) and on human IgG preparations used for therapeutic intravenous injections (IVIg) and which contain natural antibodies. These findings suggest that monoclonal immunoglobulins could arise from the proliferation of a clone that normally produces a natural antibody. The existence of common idiotype(s) between monoclonal immunoglobulins and IVIg could be relevant to the improvement noted after treatment with IVIg in patients suffering from peripheral neuropathies associated with monoclonal gammopathy.

Animals↗
PubMed1993

T cell activation by autoantigens in multiple sclerosis.

A panel of autoantigens (myosin, actin, myelin basic protein MBP, and thyroglobulin) was used to analyze antigen recognition by the peripheral blood leukocytes (PBL) of patients with active and stable multiple sclerosis (MS), patients with other neurological diseases (OND) and healthy individuals. The immune responsiveness was studied by examining the in vitro cell proliferation and the increase in the expression of two T-cell-surface activation markers (the interleukin-2 receptor IL-2R, and a late activation antigen recognized by the 19.2 monoclonal antibody). In MS, autoantigen recognition occurred more frequently than in the other groups and it was manifested by moderate proliferation or marked elevation of the expression of the IL-2R, whereas autoantigen recognition in the other groups concerned essentially the expression of the late activation antigen. Results similar to those described above were obtained with enriched T lymphocytes either in the presence or absence of IL-2. Our results suggest that the peripheral immune system in MS patients may recognize and can be activated by different autoantigens and not only by MBP, and that this response is quantitatively and qualitatively different from that of PBL from OND patients and healthy individuals.

Actins↗