Naturally occurring autologous anti-idiotypic antibodies. Participation in immune complex formation in selective IgA deficiency

Internal-image anti-idiotype HIV-1gp120 antibody in human immunodeficiency virus 1 (HIV-1)-seropositive individuals with thrombocytopenia

Anti-CD4 antibody was found in 30% of human immunodeficiency virus (HIV-1)-seropositive thrombocytopenic patients compared with 5% of nonthrombocytopenic seropositive patients (chi 2 = 21.7, P less than 0.001) and was shown by the following observations to contain internal-image anti-idiotype antibody (Ab2) directed against the antibody (Ab1) to gp120, the HIV-1 envelope glycoprotein that binds to CD4: (i) affinity-purified anti-CD4 (Ab2) bound to affinity-purified anti-HIV-1gp120 (Ab1) on solid-phase radioimmunoassay, and binding could be blocked by recombinant CD4 (rCD4) as well as recombinant gp120 (rgp120); (ii) F(ab')2 fragments of Ab1 inhibited the binding of Ab2 to rCD4; (iii) Ab2 inhibited the binding of Ab1 to HIV-1 beads; (iv) Ab2 inhibited the binding of Ab1 to gp120 on immunoblot; (v) Ab2 bound to the CD4 receptor on a CD4-bearing T-cell line, H9; (vi) Ab3 (anti-rgp120) could be produced in vivo by immunizing mice with Ab2, and binding of Ab3 to rgp120 could be blocked with rCD4; and (vii) three different Ab2 preparations bound to two different homologous Ab1 preparations. Ab1 or Ab2 alone did not bind to platelets, whereas the idiotype-anti-idiotype complex did bind to platelets in a concentration-dependent manner. Binding of the internal-image complex was 10-fold greater than that of a non-internal-image Ab1-Ab2 complex composed of anti-HIV-1gp120 and anti-anti-HIV-1gp120. Thus, patients with HIV-1 thrombocytopenia contain internal-image idiotype-anti-idiotype complexes that could be affecting CD4 cell number or function, inhibiting HIV-1 binding to CD4 cells or contributing to HIV-1 thrombocytopenia.

Relationship between naturally occurring human antibodies to casein and autologous antiidiotypic antibodies: implications for the network theory

Previous studies on human autologous antiidiotypes have been based largely upon analyses of autoimmune disease. We have previously described polyclonal, naturally occurring human autoantibodies directed against antibodies with specificity toward bovine casein in the sera of IgA-deficient humans. In order to define this system more exactly we have not produced two murine monoclonal antibodies directed against bovine milk kappa-casein to use as clonal tools to identify specific antiidiotypes in these human sera. Kappa-casein is an important part of the casein micelle in milk and cheese; in addition to being an important immunogen for man, kappa-casein is known to have conserved amino acid sequence and two antigenic epitopes. Data presented here show that the serum of up to 74% of IgA-deficient and 10% of normal humans have specific autologous antiidiotypes in their serum which bind to monoclonal antibodies directed to bovine kappa-casein. These human antibodies [intact or F(ab)'2] can be blocked from binding to the monoclonal anti-kappa-caseins by pure bovine kappa-casein or the kappa-casein peptide fragment. In contrast to previous studies in autoimmune disease, serum levels of the autoantiidiotypes were directly proportional to the level of IgG antibody to bovine kappa-casein. These observations suggest that continual exposure to a ubiquitous dietary antigen may produce an antigen driven system in which stimulation of both Ab1 and Ab2 occurs in concert.

Anti-idiotypic antibodies in patients with monoclonal gammopathies: relation to the tumour load

The production of anti-idiotypic antibodies from Epstein-Barr virus transformed peripheral blood lymphocytes was analysed in 12 patients with multiple myeloma and monoclonal gammopathy of undetermined significance. A low anti-idiotype production was found in patients with advanced disease (multiple myeloma stage III), whereas the production was high in patients with multiple myeloma stage I and monoclonal gammopathy of undetermined significance (MGUS) (P less than 0.01). The study supports the existence of an immunological network response in patients with monoclonal gammopathies.

Interfaces of the yeast killer phenomenon

A new prophylactic and therapeutic antimicrobial strategy based on a specific physiological target that is effectively used by killer yeasts in their natural ecological competition is theorized. The natural system exploited is the yeast killer phenomenon previously adopted as an epidemiological marker for intraspecific differentiation of opportunistic yeasts, hyphomycetes, and bacteria. Pathogenic microorganisms (Candida albicans) may be susceptible to the activity of yeast killer toxins due to the presence of specific cell wall receptors. On the basis of the idiotypic network, we report that antiidiotypic antibodies, produced against a monoclonal antibody bearing the receptor-like idiotype, are in vivo protecting animals immunized through idiotypic vaccination and in vitro mimicking the antimicrobial activity of yeast killer toxins, thus acting as antibiotics.

Regulation of immunity to extraembryonic antigens in human pregnancy

Pregnancy results in the immunologic challenge of the female to a wide variety of allogeneic antigens. Particular attention has been given to antibodies directed to allotypic trophoblast antigens (TLX), for trophoblast form the true allograft interface between mother and fetus. Studies found that antibodies to paternal TLX allotypes are produced in women suffering from secondary recurrent abortions. These TLX antibodies are not directed to classical HLA private epitopes. In this report, treatment of lymphocytes with papain to remove HLA Class I did not decrease TLX antigen densities. These results suggest TLX antibodies are not directed to Class I epitopes, public or private. The allotypic nature of TLX antigens requires that a pregnant female must be able to regulate TLX immune responses to avoid rejection of the conceptus. One mechanism to specifically and systemically regulate TLX immunity is the idiotype anti-idiotype network. We provide preliminary evidence in this report for the presence of TLX idiotype network in a normal primigravida. Initially, no antipaternal TLX antibodies were detected in the serum of the primigravida, suggesting no TLX immunization had occurred. However, separation of Ab1 from Ab2 by absorption of primigravida serum with 2 degrees aborter Ab1 resulted in seroconversion. The primigravida's Ab1 was cytotoxic for paternal and 3rd-party lymphocytes in a non-HLA-restricted pattern. Primigravida's Ab2 was recovered from the Ab1 matrix by competitive elution by using platelets as source of TLX antigen. The Ab2 was found to inhibit cytotoxicity by 2 degrees aborter Ab1 as well as primigravida Ab1. This is evidence that the Ab2 recognizes a cross-reactive idiotype (CRI) on TLX antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Human polyclonal and monoclonal IgG and IgM complement 3 nephritic factors: evidence for idiotypic commonality

Complement 3 nephritic factors (C3NeF) were isolated from the sera of patients with membranoproliferative glomerulonephritis (MPGN) and the supernatants of pokeweed mitogen-stimulated mononuclear cells from patients with MPGN. Three human monoclonal C3NeF antibodies (two IgGs, CK and PH, and one IgM, K3C4) were established. Using an exhaustive series of affinity columns, we isolated anti-C3NeF idiotypic antibodies (anti-IdNeF) (three from normal and two from patient sera). Anti-IdNeF preparations bound to F(ab')2-NeF and prevented its ability to stabilize C3bBb convertase. We have used the above reagents to address questions on the genesis and the diversity of C3NeF antibodies. The following results were obtained: All anti-IdNeF preparations bound to C3NeF isolated from patient sera, cell culture supernatants, and IgG and IgM monoclonal C3NeF. None of the monoclonal C3NeF bound to an extensive battery of common antigens, including Fc portion of IgG, TNP, beta-galactosidase, DNA, and bacterial products. These data indicate that C3NeF express one common idiotype and that these antibodies are not raised in response to an obvious antigen.

Identification of anti-idiotypic antibody in dogs

There is general agreement that idiotype/anti-idiotype (id/anti-id) networks are important mechanisms of immune regulation, based primarily on studies conducted using inbred laboratory animals. To determine if anti-idiotypic antibody (anti-id) could be induced during an immune response in outbred dogs, the dogs were immunized to the hapten-carrier combination dinitrophenol-ascaris (DNP-ASC) and subsequently immunized with autologous antibody in complete Freund's adjuvant (CFA). Auto-anti-id was detected in three of five dogs during the DNP-ASC response. A cross-reactive anti-id was detected in dogs immunized with autologous antibody when a mouse monoclonal antibody was used as the id. These experiments further suggest that the regulation of the immune response via network interaction, as first illucidated in inbred animals, may occur in dogs.

Human immune response to allergens of house dust mite, Dermatophagoides pteronyssinus. V. Auto-anti-idiotypic antibody characterization and cross-reactivity

From the serum of 10 allergic subjects we have prepared IgG antibodies recognizing idiotopes carried by specific antibodies to Dermatophagoides pteronyssinus (Dpt) allergens, and studied cross-reactivity of anti-Dpt IgG bystander and antigen-binding site-associated idiotopes by latex agglutination assays. Idiotopes of specific anti-Dpt IgE were evaluated by radioimmunoassays. Depending on the assay, a binding or inhibition of more than 50%, as compared to the reactivity of specific antibodies with the corresponding anti-idiotypic (anti-Id) IgG, was considered significant. Cross-reactivity of antigen-binding site-associated idiotopes attained a mean proportion of 6/10 for IgG and 9.6/10 for IgE. By contrast, bystander idiotopes cross-reacted only occasionally with a mean proportion of 2/10 for both IgG and IgE antibodies. Anti-Id antibodies from two subjects have been isolated by adsorption on insolubilized anti-Dpt antibodies of the corresponding patient. Using this purified material we have confirmed that (a) the majority of anti-Id antibodies carry an "internal image" of the initial antigen and compete in a dose-dependent manner with Dpt allergens for the binding to the anti-Dpt antibodies and (b) paratope-associated idiotopes of anti-Dpt antibodies are shared by unrelated individuals.

Detection of parasite related antigens associated with conglutinin binding immune complexes in patients with Schistosoma haematobium

An ELISA assay was designed to detect the presence of parasite related antigens associated with circulating immune complexes in patients affected by urinary schistosomiasis. The assay makes use of bovine conglutinin as the immune complex recognition unit and of human anti-Schistosoma antibody as the antigen recognition unit. Using this method we showed that 10 of 15 (67%) patients with a positive polyethylene glycol assay had circulating immune complexes in which parasite antigens could be detected.

An idiotope-specific autoantibody in SLE

The public idiotype Id-16/6 and the public idiotope Id-LLa were originally defined on the same human monoclonal anti-DNA antibody, but they are also known to occur separately on other anti-DNA antibodies. We sought the presence of these immunoglobulin variable region markers in purified immunoglobulins from the serum of nine patients with systemic lupus erythematosus (SLE) and 33 healthy donors. Sera from five patients were positive for Id-16/6, and five were positive for Id-LLa. The immunoglobulin preparations were passed over a Sepharose-Id-16/6 column in order to recover auto-anti-idiotypes. An eluate of that column was obtained from the immunoglobulin preparation of one patient whose serum was Id-16/6+ and Id-LLa-. This eluate was shown by competition assay to bind to IdLLa. This is the first demonstration of spontaneously arising human auto-anti-idiotypes against a specific idiotypic system in SLE. The results suggest that antibodies against the Id-LLa idiotope may play a role in immunoregulation.

Human immune response to allergens of house dust mite, Dermatophagoides pteronyssinus. IV. Occurrence of natural autologous anti-idiotypic antibodies

IgG isolated from the plasma of seven individuals hypersensitive to the common house dust mite Dermatophagoides pteronyssinus (DPT) was exhaustively adsorbed onto insolubilized DPT. The unbound fraction was found by radioimmunoassay to contain antibodies recognizing the variable region of both anti-DPT IgG and IgE antibodies. This recognition was idiotype (Id)-specific as it persisted after passage over insolubilized polyclonal IgG of unrelated specificity. Most of these anti-Id IgG carried the internal image of the initial antigen in that they competitively inhibited the binding of anti-DPT antibodies to DPT. Immunoadsorption of anti-Id IgG onto insolubilized anti-DPT IgG antibodies from the same individual completely eliminated their reaction with anti-DPT IgG but not with anti-DPT IgE, suggesting that idiotopes included in the antigen-binding site of specific IgG and IgE antibodies were not identical. Anti-Id IgG recognizing idiotopes located outside the antigen-binding site (bystander idiotopes) were also completely removed by passage over insolubilized anti-DPT IgG; in this case the reaction of the anti-Id IgG with both anti-DPT IgG and anti-DPT IgE was inhibited, indicating that, for a given individual, bystander idiotopes were shared between anti-DPT antibodies pertaining to these two isotypes.

Evidence for circulating IgE complexes in food allergy

Antigen entry and the formation of immune complexes occur in atopic subjects after food ingestion. We have studied patients with asthma, eczema and arthralgia and we were able to detect the presence of IgE immune complexes and the antigen entry from the gut before and after food challenge. Food allergic subjects showed, after food challenge, the presence of IgE and IgG immune complexes, which correlates with the subsequent occurrence of symptoms. Both the symptoms and the appearance of IgE immune complexes could be prevented by pretreatment with oral sodium cromoglycate (SCG). IgE immune complexes were isolated by an isokinetic ultracentrifugation gradient and the components were analyzed for antigen-specific IgE and IgG as well as free antigen levels. The observation that SCG reduces antigen entry, the appearance of IgE immune complexes and the occurrence of symptoms point to the central role of IgE in the intestinal mucosa.

Anti-TSH antibody with high specificity to human TSH in sera from a patient with Graves' disease: its isolation from, and interaction with, TSH receptor antibodies

A patient with thyrotoxic Graves' disease had an apparent measurable level of serum TSH (2.5 microU/ml) by double-antibody radioimmunoassay (RIA). The serum IgG bound with both [125I]human(h)TSH and [125I]bovine(b)TSH. The [125I]hTSH binding was more effectively displaced by human than bovine TSH, whereas [125I]bTSH binding was displaced exclusively by bTSH. Scatchard analyses revealed that [125I]hTSH binding showed two components, whereas [125I]bTSH binding had only one component. Serum TSH determined by RIA became undetectable 21 months after antithyroid drug treatment with a parallel decrease of [125I]hTSH binding IgG activity. Four thyrotrophin binding inhibitory immunoglobulins (TBII) from other patients did not interfere with the binding of the patient's serum to [125I]h- or bTSH. Furthermore, the in-vitro thyroid stimulating activities of three thyroid stimulating antibodies (TSAb) were not affected by the addition of this patient's IgG. On the other hand, this patient's Ig (3 mg/ml) abolished the in-vitro thyroid stimulation by bTSH (100 microU/ml), but did not affect that by hTSH (100 microU/ml). The anti-hTSH antibody, TSH receptor antibody and anti-bTSH antibody in the serum, which contains TSAb as well as anti-TSH antibodies, could be partially purified by hTSH-agarose and subsequently by guinea pig fat cell membrane affinity absorptions. However, the anti-hTSH antibody fraction obtained had both hTSH binding activity and thyroid stimulating activity, and this fraction did not show any inhibitory effect on the in-vitro thyroid stimulation of autologous TSH receptor antibody or hTSH. The possible significance of anti-TSH antibodies is discussed.

Interaction between anti-DNA and anti-DNA-binding protein autoantibodies in cryoglobulins from sera of patients with systemic lupus erythematosus

We have previously shown that sera from some patients with SLE and related disorders contain autoantibodies to a DNA-binding protein complex designated p70/p80. The present study shows that anti-p70/p80 autoantibodies are frequently accompanied by anti-DNA antibodies and cryoglobulins. When the cryoglobulins were isolated, they were found to be specifically enriched in both anti-p70/p80 and anti-DNA activities. The anti-p70/p80 and anti-DNA antibodies were found to be distinct populations of autoantibodies rather than a single crossreactive species, since they could be separated from one another by chromatography on DNA-cellulose. Certain human anti-DNA mAbs could inhibit the binding of autoimmune polyclonal anti-p70/p80 antibodies to p70/p80, suggesting that anti-DNA antibodies might also associate with the variable regions of some anti-p70/p80 antibodies in the cryoglobulins. Binding of one murine anti-p70/p80 mAb (111-12) also was inhibited by certain human anti-DNA mAbs, but the binding of another murine mAb (162-11) to a different epitope of p70/p80 was not. These studies suggest that certain anti-DNA antibodies may interact with the variable regions of a population of anti-p70/p80 antibodies. The cryoglobulins found in the sera containing both anti-p70/p80 and anti-DNA antibodies may represent immune complexes consisting, in part, of idiotype and antiidiotype.

Studies of immune responses in mice prone to autoimmune disorders. II. Decreased down-regulation by auto-anti-idiotype antibody in autoimmune-prone mice

Three lines of evidence are presented which suggest that autoimmune-prone mice are deficient in the production of auto-anti-idiotype antibody during their immune response to trinitrophenylated Ficoll (TNP-F). NZB, MRL lpr/lpr and older BXSB male mice have no hapten-augmentable plaque-forming cells (PFC). Hapten-augmentable PFC have been previously shown to be cells whose secretion of antibody has been inhibited by the binding of auto-anti-idiotype antibody to cell surface idiotype. Sera from TNP-F immunized NZB mice lack PFC inhibiting activity (anti-idiotype antibody). Spleen cells from TNP-F immune NZB mice fail to transfer anti-idiotype antibody-mediated suppression to naive mice as do spleen cells from immune non-autoimmune-prone mice. Taken together these data suggest that autoimmune-prone mice are deficient in auto-anti-idiotype antibody-mediated downward regulation of their immune responses. It was further shown that the immune response of NZB mice to TNP-F shows a slower decline in splenic PFC and a greater heterogeneity of PFC affinity than do the responses of non-autoimmune-prone strains. Since athymic (nude) mice, which were previously shown to be defective in the production of auto-anti-idiotype antibody, also show a slower decline in splenic PFC and an increased heterogeneity of PFC affinity, it is suggested that these peculiarities of the immune responses of autoimmune-prone and athymic mice are also the consequences of the lack of auto-anti-idiotype antibody-mediated down-regulation.

Anti-Fab antibodies in humans. Predominance of minor immunoglobulin G subclasses in rheumatoid arthritis

Isoelectric focusing analyses of sera from patients with rheumatoid arthritis (RA) demonstrate two populations of antibodies directed against the Fab portion of pooled human IgG. One population is composed of polyclonal alkaline anti-Fab antibodies (alpha FABA) and the other, acidic alpha FABA which are more clonally restricted. In this study we have identified the immunoglobulin classes and subclasses of these antibodies in RA sera. Enzyme-linked immunosorbent assays (ELISA) demonstrated alpha FABA in RA sera to be predominantly IgG. A large portion of IgG alpha FABA existed as immune complexes, inasmuch as dialysis of RA sera against 6 M urea before ELISA analysis was necessary for maximal detection of alpha FABA activity. Chromatofocusing of RA sera isolated alpha FABA of different charges and revealed the acidic clonally restricted alpha FABA to be IgG4 and IgG3, whereas the polyclonal alkaline group contained IgG1, IgG2, and IgG3. Overall, acidic IgG3 and IgG4 comprised 70% of IgG alpha FABA, and high levels of IgG4 were seen in most RA sera. When alpha FABA were elevated in normal sera, they were primarily of the IgG4 subclass, and also existed as immune complexes. Serum anti-Fab activity was removed by adsorption of sera with Fab fragments. Anti-Fab antibodies of both kappa and lambda light-chain types were present in RA sera, and F(ab')2 fragments of RA serum immunoglobulin were found to possess anti-Fab activity. These studies indicate that alpha FABA in RA sera are limited to the IgG class, and that most of these antibodies exist as immune complexes and display clonal and minor IgG subclass restriction.

Cross-reactive idiotypes in immunoglobulin A-deficient sera

Mice of inbred strains immunized with simple antigens can produce antibodies that share similar V regions, which result in serologic similarities called cross-reactive idiotypes (CRI). In this study, we considered the possibility that IgA-deficient humans, who are continuously immunized via the intestinal tract by dietary protein, might also produce antibodies sharing CRI. For this, anti-casein antibodies were isolated from the blood of 16 adult IgA-deficient donors (4 Finns and 12 North Americans) and an autologous anti-anti-casein from the blood of one of the Finnish donors. In addition, a heterologous anti-anti-casein was raised to the casein-anti-casein immune complexes of this donor. Comparing the activities of the two anti-idiotypes, it was found that both bind anti-casein in the region of the antigen binding site, but that each binds additional determinants not located within this region, with the heterologous reagent having more affinity for these latter determinants than the autologous anti-idiotype. Using both reagents in enzyme-linked immunosorbent assay inhibition assays, extensive cross-reactivities between anti-caseins were demonstrated. Using the autologous anti-idiotype, 5 of 16 anti-caseins were found to share CRI, and with the heterologous reagent 12 of 16 shared CRI. In both assays, the anti-caseins of Finnish donors displayed more cross-reactivity than those derived from Northern American donors. These studies show that specific, commonly shared CRI can be identified in this human system in which antibodies are raised as a result of natural immunization across the gastrointestinal mucosa.

Acquired C1-inhibitor deficiency associated with antiidiotypic antibody to monoclonal immunoglobulins

The syndrome of acquired angioedema and C1-inhibitor deficiency is associated with B-cell lymphoproliferative disease. It is characterized by accelerated consumption of C1q and C1 inhibitor in vivo and by low levels of serum C2 and C4. Four patients with B-cell malignant diseases (IgA myeloma, macroglobulinemia, chronic lymphocytic leukemia, and B-cell lymphoma, respectively) and acquired C1-inhibitor deficiency were found to have circulating antiidiotypic antibodies to the monoclonal immunoglobulin expressed on the surface of their B cells (three patients) or in the cytoplasm of their bone-marrow cells (one patient). Two of the four patients had circulating M components, and their antiidiotypic antibodies reacted with the M components. In three patients studied the percentage of B cells bearing C1q was 18, 24, and 35 per cent, as compared with 2.3 +/- 1.7 per cent (mean +/- S.D.) in six normal controls. These results suggest that an interaction between the idiotype of monoclonal immunoglobulins and antiidiotypic antibodies causes increased consumption of C1q and C1 inhibitor in patients with acquired angioedema and C1-inhibitor deficiency. We propose that the subsequent activation of the early components of complement leads to increased vascular permeability and to angioedema and that these patients have a disease caused by antiidiotypic antibodies.

Idiotypic-antiidiotypic interactions in man

Anti-idiotypic (anti-Id) antibodies are directed against antigenic determinants expressed by the antigen-binding region of the immunoglobulin molecules. Their interaction with antigen receptors on immune cells modulates the immune response. In man auto-anti-Id antibodies have been demonstrated. These antibodies not only participate in the regulation of the immune response, but can result in disease as in the case of acquired angioedema with B cell malignancy and possibly in autoimmune diseases. Anti-Id antibodies may be useful tools in cancer immunotherapy and in the production of vaccines.

The effect of monoclonal antibodies against Escherichia coli type 1 pili and capsular polysaccharides on the interaction between bacteria and human granulocytes

Monoclonal antibodies against Escherichia coli type 1 pili and the K13 capsular polysaccharide strongly influenced the interaction between human polymorphonuclear leucocytes (PMNL) and E. coli 06:K13:H1. Bacteria with type 1 pili, associated with the neutrophils, caused a metabolic activation but were not ingested. Addition of monoclonal antibodies to type 1 pili resulted in increased association, but also phagocytosis and metabolic activation of the granulocytes. Monoclonal antibodies against the K13 polysaccharide strongly stimulated phagocytosis, especially of the type 1 piliated bacteria, suggesting a synergistic effect between binding of type 1 pili and the Fc part of the capsular antibodies to the PMNL. Addition of D-mannose inhibited the opsonization of type 1 piliated E. coli 06:K13:H1 in the presence of both type 1 pilus antibodies and capsular antibodies. Monoclonal anti-idiotypic (anti-anti-capsular) antibodies reduced the association with the PMNL of the bacteria preopsonized with anti-capsular antibodies. The bacterial ingestion and the metabolic activation of the PMNL were also reduced, suggesting a role for anti-idiotypic antibodies in specific modulation of inflammation.

Idiotypic network: possible explanation of seronegativity in a patient with rheumatoid arthritis

In order to explain long term seronegativity in certain patients with rheumatoid arthritis (RA), we looked for the presence of anti-idiotypic antibodies against rheumatoid factors (RFs). From a patient's serum with classical but seronegative RA, we isolated a low quantity of the IgG fraction which partially recognized polyclonal RF idiotypes. The purified Fab'2 anti-idiotypic antibodies were able to inhibit up to 48% of in vitro RF production by pokeweed mitogen stimulated lymphocytes from a patient's peripheral blood with seropositive RA. The two main conclusions of this study are: (1) this single patient with seronegative RA has serum antibodies directed against RF idiotypes and (2) these anti-idiotypic antibodies could be implicated in the generation of seronegativity.

Immune complexes in IgA nephropathy: presence of antibodies against diet antigens and delayed clearance of specific polymeric IgA immune complexes

Several features suggest that IgA nephropathy is an immune complex (IC)-mediated disease. The source of antigen(s) is unknown but the predominant involvement of IgA suggest that it is associated in some way with the gut or respiratory tract. Taking into account the specific hepatobiliary transport by polymeric IgA of circulating antigens entering through the mucosal surfaces we examined the possible involvement of antibodies against food antigens in the circulating IC and the existence of a defect in their blood clearance in patients with IgA nephropathy. A rise in multimeric IgA-IC (Raji assay) occurred in three of seven control subjects with a peak at 2-4 h after food ingestion. The amount of multimeric IgA-IC present at fasting in four out of six patients, diminished 2-4 h after food challenge, reaching a new peak around 6 h. At fasting, three out of six patients had IC containing antibodies against diet antigens (e.g. ovalbumin). These IC paralleled, both in patients and controls, the levels of multimeric IgA-IC. In patients small multimeric IgA-IC predominated at fasting and 24 h after food ingestion, while larger IC were detected at 2-4 h of food challenge. The specific polymeric IgA-IC showed in controls a maximal peak with similar distribution to that of multimeric IgA-IC, but with a quicker disappearance from the circulation. By contrast, polymeric IgA-IC remained elevated 24 h after food ingestion in most patients. These results suggest that antibodies against common antigens are within circulating IC and that a defect in the hepatic clearance of circulating polymeric IgA-IC exists in patients with IgA nephropathy.

Evidence for a disease specific antigen in circulating immune complexes in ankylosing spondylitis

The presence of circulating immune complexes (CIC) has been documented in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and ankylosing spondylitis (AS) by various investigators. It has been suggested that these may be used as probes to identify antigens playing a role in these pathological processes. Using a solid-phase cross-reaction assay to establish if these complexes reacted with each other in specific disease groups, it was found that polyethylene glycol (PEG) precipitates of six AS patients cross reacted in 29 of 36 tests, but reacted with SLE and RA PEG precipitates in only two of 24 tests in each case. SLE PEG precipitates cross-reacted in four of 14 tests and reacted with none of the six AS and four RA precipitates. Similarly, RA PEG precipitates did not cross-react (none of 16 tests), nor did they react with AS (none of 24 or SLE precipitates (none of 16). Similar results were observed when IgG, obtained after acid dissociation on sucrose density gradients of CIC isolated by PEG precipitation and staphylococcal protein A chromatography, was used as the solid phase component. F (ab')2 fragments with similar antibody specificity were obtained by pepsin digestion of isolated CIC from three of six AS patients. These bound radiolabelled AS PEG precipitates (2.02-2.40%) significantly more than SLE (0.22-0.28%) or RA (0.29-0.35%) precipitates. These studies demonstrate the feasibility of obtaining F (ab')2 fragments with antibody activity from isolated CIC and the presence of a disease specific antibody specificity in AS CIC. The nature of the antigen involved remains to be elucidated. Such a cross-reactive antibody specificity was not found in RA nor SLE CIC.

Antiidiotype stimulation of antigen-specific antigen-independent antibody responses in vitro. I. Evidence for stimulation of helper T lymphocyte function

Antibodies specific for the idiotypes of B10 anti-(T,G)-A-L antibodies (anti-Id) induced in vivo (T,G)-A-L-primed lymphocytes to secrete anti-(T,G)-A-L antibodies in vitro in the absence of antigen. Responses to anti-Id were quantitatively and qualitatively similar to responses to antigen. Responses were specific in that: (a) only lymphocytes primed in vivo with (T,G)-A-L (but not other antigens or unprimed cells) were inducible; (b) only anti-Id (but not a variety of control antibodies) induced responses; and (c) only anti-(T,G)-A-L antibodies were secreted. Antigen-primed T lymphocytes mixed with unprimed B plus accessory cells also responded to anti-Id and the phenotype of the responding T cells was Lyt-1+, Lyt-2-. Supernatants obtained from antigen-primed T cells incubated for 3 d with anti-Id (but not when incubated with controls) provided help to unprimed B plus accessory cells in the presence of anti-Id, thus providing direct evidence for induction of T lymphocyte helper function by anti-Id. In contrast to responses to (T,G)-A-L, responses to anti-Id did not appear to be regulated by H-2-linked Ir genes. The system described is a powerful tool for delineation of the mechanisms whereby antiidiotype antibodies affect lymphocyte function.

Characterization of anti-Fab' antibodies in human sera: identification of soluble immune complexes that contain hidden anti-KLH and blocking anti-immunoglobulins following immunization with keyhole limpet haemocyanin

After immunization with keyhole limpet haemocyanin (KLH), increased concentrations of anti-KLH and anti-Fab' antibodies (Abs) were demonstrated in sera from 18 of 20 volunteers. In many cases, post-immunization sera contained soluble immune complexes that incorporated both anti-Fab' and 'hidden' or 'blocked' anti-KLH antibodies. The complexes containing hidden anti-KLH and blocking anti-Fab' Abs were not found in pre-immunization sera. The hidden Abs to KLH were revealed by demonstrating increases in anti-KLH activity in sera incubated previously with Fab' fragments, immobilized on plastic microtitre tray wells. Incubation with insoluble Fab' did not influence the quantity of anti-tetanus toxoid (TT) that was detected in these sera. Addition of affinity purified anti-Fab' Abs to samples, previously 'unblocked' by adsorption with immobilized Fab', depressed their anti-KLH activity to levels present before adsorption, but did not change the quantity of Abs to Dermatophytin, Trychophyton, or TT therein. These results suggest that some autoantibodies generically recognized as 'Fab' specific' have properties that are usually considered to be characteristic of autoanti-idiotypes.

Production of auto-anti-idiotypic antibody during the normal immune response. VI. Hapten augmentation of plaque formation and hapten-reversible inhibition of plaque formation as assays for anti-idiotype antibody

(1) Evidence has been presented that the detection of hapten-augmentable plaques indicates cells whose secretion of antibody had been blocked by the binding of auto-anti-id to cell surface idiotypes. Because of the dependence of the assay on the affinities of the various species for one another, the number of hapten-augmentable plaques detected should be regarded as a minimal estimate of the number of cells whose secretion of antibody is inhibited by auto-anti-id. For confirmation that hapten-augmentable PFC are due to auto-anti-id 2 principal controls are important: (a) incubation of the spleen cell population with hapten prior to plaquing should remove the hapten-augmentable PFC; (b) the dialyzed supernate from hapten incubated cells should inhibit plaque formation in a hapten-reversible manner. (2) Evidence has been presented that hapten-reversible inhibition of plaque formation can serve as an assay for anti-id. Apparent false positive assays can result from the presence of anti-hapten antibody or antigen-antibody complexes; however, these apparent false positives are rarely reversed by hapten. Removal of anti-hapten antibody, by passage over an antigen immunoadsorbent, will eliminate this source of false positives and the procedure is recommended. False negative results can arise from mismatching of the anti-ids in the sample to be assayed and the idiotypes of the target cells used in the assay. This can result from shifts in idiotype expression related to age and time after antigen injection. False negatives can also result from the presence of idiotype-anti-id complexes in the sample to be assayed. This source of false negatives can sometimes be eliminated by passage of the sample through an antigen immunoadsorbent.

Naturally occurring anti-idiotypic antibodies in myasthenia gravis patients

Aberrant regulation of the immune system can lead to the development of autoimmune diseases such as myasthenia gravis. Autoantibodies against the nicotinic acetylcholine receptor (AChR) are found in the serum of myasthenia gravis patients and trigger a reduction of AChR at the muscle endplate resulting in increased muscle fatiguability. It is possible that the autoimmune response results from altered idiotype anti-idiotype network interactions. Here we have used a monoclonal anti-AChR antibody (ACR-24, gamma 1, kappa) in an enzyme-linked immunoabsorbent assay (ELISA) to measure anti-AChR immunoglobulin in human sera. In this assay, ACR-24 is attached to microtitre plates followed by the addition of solubilized human AChR which is bound by the immobilized ACR-24. However, during the development of this assay, it was observed that certain myasthenic patients appeared to have antibodies which bound to ACR-24 alone. This unexpected finding suggested that we had discovered naturally occurring anti-idiotype antibodies in myasthenic sera.

Naturally induced auto-anit-idiotypic antibodies. Induction by identical idiotopes in some members of an outbred rabbit family

Naturally induced auto-anti-idiotypic (AAI) antibody responses specific for antimicrococcal antibody idiotypes were detected in 42% of the rabbits in a family immunized with Micrococcus lysodeikticus. The natural AAI response of each rabbit recognized only a portion (11-41%) of that individual's total antimicrococcal antibody population. Cross-reactions of idiotypes were observed within the group of rabbits exhibiting natural AAI responses. Examination of the basis for the cross-reactions showed that the natural AAI antisera recognized identical idiotopes on the antimicrococcal F(ab')2 fragments from each rabbit that made an AAI response. The cross-reactive idiotopes were shown to be of paternal origin and were found in the antimicrococcal antibodies of each offspring. The data strongly support the idiotypic network concept that naturally induced AAI responses may occur routinely in outbred normal individuals as a result of antigenic stimulation. Further, the data suggest that the induction of regulatory AAI antibody responses in outbred rabbits may depend on the expression of particular germ line idiotopes.