Detection of anti-histone activity in sera of patients with monoclonal gammopathies

Autoantibodies in breast cancer

In addition to their historical role, autoantibodies appear promising as biomarkers to facilitate diagnosis, improve patient outcome and decrease mortality in cancer. Autoantibodies may also be useful in the identification of subjects at risk for cancer, that is, those bearing premalignant changes. Numerous studies have demonstrated that cancer serum contains a variety of autoantibodies that react with autologous cellular antigens, that is, tumor-associated antigens. Interestingly, some of these antigens are involved in signal transduction, cell cycle regulation, cell proliferation, and apoptosis. As such, identification of these molecules has additional importance for development of novel anticancer drugs and vaccines. This review focuses on the use of autoantibodies in breast cancer, a major public health problem. We also address the need for additional research to validate this approach in cancer diagnostics and therapeutics in general.

Serologic laboratory findings in malignancy

Autoantibodies are extremely promising diagnostic and prognostic biomarkers of cancer, and have the potential to promote early diagnosis and to make a large impact by improving patient outcome and decreasing mortality. Moreover, autoantibodies may be useful reagents in the identification of subjects at risk for cancer, bearing premalignant tissue changes. Great efforts are being made in many laboratories to validate diagnostic panels of autoantibodies with high sensitivity and specificity that could be useful in a clinical setting. It is likely that prospective studies of sufficiently large cohorts of patients and controls using high-throughput technology may allow the identification of biomarkers with diagnostic significance, and perhaps of discrete antigen phenotypes with clinical significance. The identification of TAAs may also be essential for the development of anticancer vaccines, because autoantibodies found in cancer sera target molecules involved in signal transduction, cell-cycle regulation, cell proliferation, and apoptosis, playing important roles in carcinogenesis. On this basis, molecular studies of antigenantibody systems in cancer promise to yield valuable information on the carcinogenic process. TAAs identified by serum antibodies in cancer sera can be natural immunogenic molecules, useful as targets for cancer immunotherapy. An important problem encountered in the practice of medicine is the identification of healthy individuals in the general population who unknowingly are at high risk of developing cancer. For the rheumatologist, a related problem is the identification of those patients with rheumatic diseases who are at high risk for developing a malignant process. These problems encountered in the fields of cancer and the rheumatic diseases can in the future be helped by new diagnostic instruments based on antibodies. The need for promoting the early diagnosis of cancer is a recognized major public health problem in need of significant research support for the validation of multiple promising but inconclusive studies, with the intention of producing diagnostic panels of autoantibodies in various types of cancers. Cancer developing in patients with rheumatic diseases is also an important problem requiring prospective longterm follow-up studies of patients with rheumatic diseases, particularly because some of the new biologic therapies seem to increase the cancer risk. It is possible that a panel of autoantibodies common to patients with cancer and the rheumatic diseases may prove to be of value in the identification of those patients with ADs at high risk for neoplasms.

Artifactual laboratory abnormalities in patients with paraproteinemia

Paraproteinemia, most often as a result of monoclonal gammopathy of unknown significance (MGUS), is very common and its prevalence is expected to increase with the aging of the population. Paraproteins can be associated with a variety of laboratory abnormalities. These may occur as a result of the underlying disease process that causes paraproteinemia, or may result from the paraproteins affecting a physiologic function in vivo. Laboratory abnormalities may also occur artifactually as a result of interference by the paraproteins with a laboratory test in vitro. A wide variety of laboratory tests may be affected, including several commonly obtained tests such as blood counts, serum sodium, calcium, phosphorous, and high-density lipoprotein (HDL) cholesterol. There is poor correlation between the concentration or type of paraproteins and the likelihood of interference. Awareness of this possibility is important so as to avoid erroneous diagnostic conclusions or unnecessary testing.

Antiribosomal-P protein antibodies in a patient with systemic lupus erythematosus and non-Hodgkin's lymphoma: more than coincidental finding?

Patients with systemic lupus erythematosus (SLE) are at an increased risk of lymphomas, but mechanisms underlying this association are obscure. Recently, it has been shown that antiribosomal-P protein (anti-P) antibodies cross-react with phospholipids and enhance the production of cytokines which may influence lymphomagenesis. We report a 46-year-old woman who suffered high grade diffuse large B-cell non-Hodgkin's lymphoma (DLBCL) 28 months after the diagnosis of SLE. Development of lymphoma was associated with occurrence of serum monoclonal IgM, and pronounced prolongation of phospholipid-dependent clotting tests. Anti-P IgG antibodies were highly positive both on HEp-2 cells and in ELISA test. Anticardiolipin, anti-beta2 glycoprotein I, and antiprothrombin IgM antibodies have also been found in high concentrations. Complete remission of DLBCL and SLE, with normalisation of clotting tests, and disappearance of M component was achieved with administration of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone. The progression of SLE to DLBCL associated with presence of anti-P antibodies has not been previously reported. This association may not be coincidental, but further investigations are required to confirm this hypothesis.

Autoantibodies in patients with monoclonal gammopathies

Although autoantibody activities are rather often associated to monoclonal gammopathies, only monoclonal immunoglobulins of the IgM isotype are really directed against autoantigens that are often polysaccharides or are formed by highly repetitive structures. This strict association is frequently revealed also by clinical manifestations of the autoimmune response generated by the monoclonal macroglobulin. Most monoclonal immunoglobulins of non-IgM isotype are instead totally inactive toward self-antigens, the autoantibody activity being instead associated, if present, to polyclonal immunoglobulins. Although the same BAFF/APRIL system is involved in perpetuation of humoral autoimmunity as well as in stimulation of clonal B-cell expansion, the autoimmune commitment of B cells of a non-IgM isotype is hardly compatible with their possible involvement in an uncontrolled proliferation pathway, whose prerequisite is the homing of these B cells to the bone marrow compartment. The IgM-secreting cells appear instead to possess a much lower tendency, and/or a looser requirement, for their homing in the bone marrow prior to their actual proliferation. This may explain the quite different consequences, in terms of autoimmunity, between IgM and non-IgM paraproteinemias.

Prevalence of 13 autoantibodies and of the 16/6 and related pathogenic idiotypes in 465 patients with systemic lupus erythematosus and their relationship with disease activity

With a cross sectional study of 465 consecutive systemic lupus erythematosus (SLE) patients tested for 13 autoantibodies (Aab) and two idiotypes we determined the prevalence of Aab according to disease activity, both general and at particular organ systems. Seventy seven percent of SLE sera had at least one Aab and 56% had it at high titres. Pathogenic idiotypes had a prevalence of less than 10% and 166 sera had Aab to 5 or more antigens and 9 sera had Aab against all 13 antigens tested. Patients with active disease had increased prevalence of Aab to DNP, ssDNA, ENA, mitochondria and histones when considered at 5 s.d. above the mean of normal controls. The higher positivity of Aab in patients with active disease was confirmed in logistic regression analysis adjusted by age, disease duration, and intensity of treatment. A trend was observed of increased prevalence and titres of Aab from inactive disease without treatment, to inactive disease but still being treated, to active disease. Only 22% of patients with active disease had no Aab and the higher the number of Aab the higher the frequency of active disease. Patients with active arthritis, and to a lesser degree those with active mucocutaneous involvement, had higher prevalence and titres of most autoantibodies than patients with disease activity at other organ systems. Active renal disease associated only with anti-dsDNA, whereas active CNS disease associated with anti-mitochondrial Aab. Our findings support the vision of SLE as an immune dysregulation leading to polyclonal B cell activation with resulting production of multiple Aab. Their profiles seem influenced by genetical, hormonal and environmental factors and, in turn, they contribute to the clinical picture in each patient. Disease activity influences the presence of some, but not all, Aab and some of them may remain present in some patients, even in remission.

Natural autoantibodies in sera of patients with Gaucher's disease

Gaucher's disease (GD) is associated with hyperactivity of the immune system, which manifests by polyclonal hypergamma-globulinemia and an increased incidence of monoclonal gammopathies in GD patients. We analyzed sera of 43 patients with GD for the presence of autoantibodies against 14 autoantigens. The results demonstrated a significant increase in the incidence of all autoantibodies tested, ranging from 11% for anti-RNP, pyruvate dehydrogenase (PDH), and DNA antibodies to 57% for rheumatoid factor. The autoantibodies were of all three isotypes, namely, IgG, IgM, and IgA. There was no correlation between the levels of immunoglobulins in the serum and the titer of autoantibodies found. Immunization of naive mice with a pool of purified anti-DNA antibodies form GD patients did not result in induction of experimental systemic lupus erythematosus (SLE), suggesting that they may represent natural autoantibodies that are not pathogenic. In conclusion, we found high titers of natural, polyspecific, nonpathogenic autoantibodies in the sera of GD patients.

Identification and characterization of antimitochondrial autoantibodies in sera of patients with monoclonal gammopathies

Monoclonal gammopathies (MG) are defined by the accumulation of monoclonal immunoglobulins, a result of monoclonal B lymphocytes or plasma cell proliferative disorder. Only rarely do these antibodies cause an overt disease by binding to a specific autoantigen (e.g., factor VIII). In the present study, sera from 100 patients with MG were screened for the presence of antibodies against the mitochondrial pyruvate dehydrogenase complex (PDH) -- autoantibodies that are the hallmark primary biliary cirrhosis (PBC). Anti-PDH antibodies were found in 6 patients, all asymptomatic. Using ELISA and immunoblotting methods, it was found that the titre of the anti-PDH antibodies was relatively low (average OD +/- SD: 0.744 +/- 0.529; PBC patients: 1.225 +/- 0.291; P = 0.02). In each patient the autoantibodies were of both kappa and lambda chains, suggesting that they are of polyclonal origin and implying that in MG there is a significant production of polyclonal autoantibodies, in addition to monoclonal proliferation. Furthermore, in 5 of the 6 patients (83%) the anti-PDH antibodies did not recognize the E2 component of PDH (which is the major autoantigen in PBC) an did not inhibit the activity of PDH (which was inhibited by PBC autoantibodies). This is in concert with the fact that none of the patients developed liver disease and emphasizes the specificity of the anti-PDH autoantibodies associated with PBC.

Pathogenic natural anti-cardiolipin antibodies: the experience from monoclonal gammopathy

Anti-cardiolipin antibodies (ACA) were detected in 19% of sera from patients with monoclonal gammopathies (MG). ACA were purified from the sera of patients with MG. One of the IgG-ACA was found to be monospecific with high affinity for cardiolipin, and to carry a pathogenic ACA Id (1.10). Active immunization of naive BALB/c mice with the purified IgG-ACA was followed by production in the mice of sustained high titres of ACA, associated with prolonged activated partial thromboplastin time (APTT) (61 +/- 14s versus 31 +/- 2s in control mice; P < 0.001) and thrombocytopenia (468,000 +/- 224,000/mm3 versus 994,000 +/- 92,000/mm3 in controls; P < 0.001). The titres of other autoantibodies (e.g. anti-DNA, anti-histones), although being high after immunization, decreased rapidly and were undetected after 1 month following the boost injection. The mice immunized with the IgG-ACA exhibited low fecundity (36% of mice became pregnant versus 62% observed in the group immunized with control IgG). The pregnant mice had increased resorption rate (the equivalent of fetal loss in the human) of 52 +/- 8% (versus 5 +/- 4% in the control group). The mean (+/- s.d.) embryo and placental weights in mice with anti-phospholipid syndrome (APLS) were significantly lower compared with the mice injected with control IgG (682 +/- 304 mg and 102 +/- 12 mg versus 1303 +/- 105 mg and 145 +/- 8 mg, respectively; P < 0.001). Serum monoclonal immunoglobulins having autoantibody activity may be regarded as an expansion of clones producing natural autoantibodies. Our results confirm the pathogenic role of natural ACA in the pathogenesis of the anti-phospholipid syndrome.

The detection of antithyroglobulin activity in human serum monoclonal immunoglobulins (monoclonal gammopathies)

The sera of 159 patients with monoclonal gammopathies were examined for the presence of anti-thyroglobulin (Tg) activity. An enzyme-linked immunosorbent assay was employed. Thirty-one (19.5%) sera were found to bind Tg. The activity against Tg was further confirmed by using purified immunoglobulins and employing competition assays. The anti-Tg antibodies were found in the sera of patients with IgG, IgM and IgA gammopathies. Anti-Tg antibodies were more frequent among patients with IgG gammopathy. Autoantibodies to Tg are found in patients with Hashimoto's thyroiditis, Graves' disease and occasionally in patients with thyroid carcinoma. Natural autoantibodies directed against human Tg have been detected, as well, in healthy subjects. None of the patients in the present study whose serum was found to contain high titers of anti-Tg human monoclonal antibodies had any clinical or biochemical evidence of thyroid disease. Our results of a high incidence of anti-Tg activity in the sera of patients with monoclonal gammopathies support previous reports of autoantibody properties characteristic of these immunoglobulins.

Human CD5-positive B cells in lymphoid malignancy and connective tissue diseases

The current literature on human CD5-positive B cells (CD5 + B cells) has been analysed, with a special emphasis on non organ-specific auto-immune diseases. Malignant cells of most of the chronic lymphoid leukaemias of the B cell lineage express the CD5 molecule. Antibodies of the IgM class produced by leukaemic B cells are multispecific auto-antibodies. The CD5 + B cell subset may be expanded in non organ-specific autoimmune diseases, such as rheumatoid arthritis, primary Sjögren's syndrome, systemic lupus erythematosus. This holds true for various conditions, including organ-specific auto-immune diseases. Since auto-immune features are common in lymphoproliferative disorders, and the latter be a complication in non organ-specific auto-immune diseases, CD5 + B cells may represent an intermediary between these auto-immune diseases and B cell lymphoproliferations. Studies on the regulation of CD5 + B cell production and function are likely to shed light on the aetiology of, and pathogenetic mechanisms operating in the different disease states.

Autoantibodies in the sera of patients with lymphoma

Sera of 84 patients with Hodgkin's disease (HD) and 55 patients with non-Hodgkin's lymphoma (NHL) were examined for the presence of autoantibodies to ssDNA, dsDNA, Poly (I), Poly (G), cardiolipin, histones, RNP. Sm, Ro (SS/A), La (SS/B) and the common anti-DNA idiotype (16/6) using an enzyme-linked immunosorbent assay (ELISA). Anti-ssDNA antibodies were detected in the sera of 20 patients with lymphoma (23.8%), more among those with NHL than HD (16 vs. 4 patients p < 0.01). Anti-RNP and anti-Sm antibodies were found in 16 (21.7%) and 14 lymphoma patients (20%) respectively, significantly more than in the controls (p < 0.05) in both antibodies). These findings remained valid following subgrouping of the patients into those with HD and NHL. With all the other autoantibodies examined no significant difference could be observed in the incidence between lymphoma patients and controls. These results differ from our previous survey carried out on sera of patients with solid tumors in whom no increased frequency of any of the autoantibodies could be determined. In view of the evidence suggesting an increased risk of lymphoma in a number of autoimmune diseases our results extend this relationship to an increased incidence of autoantibodies among patients with lymphoma.

Diversity and pattern of inheritance of autoantibodies in families with multiple cases of systemic lupus erythematosus

The pattern of inheritance of autoantibodies in eight families chosen from a pool of 110 families of patients with systemic lupus erythematosus (SLE) is described. In all the eight families at least two members were already affected by SLE. In total, 19 patients and 43 first degree relatives were examined. The inheritance of a large set of antinuclear antibodies (for example, DNA, Sm, RNP, Ro, La, histones) and 16/6 idiotype seemed to be related to some unknown genetic factors but not related to HLA. The presence of numerous antinuclear autoantibodies in the serum of a subject was not necessarily associated with overt disease. The incidence of the 16/6 idiotype among patients and their relatives was low. It is not yet clear whether the 'autoantibody burden' is greater in families with multiple cases of SLE than in families with single cases.

Distribution of two common idiotypes of anticardiolipin antibodies in sera of patients with primary antiphospholipid syndrome, systemic lupus erythematosus and monoclonal gammopathies

The frequency of two common idiotypes of anticardiolipin antibodies (aCL) was determined in sera from three groups of subjects, patients with systemic lupus erythematosus (SLE), with primary antiphospholipid syndrome (PAPS) and with monoclonal gammopathies (MG), as compared to normal population. The idiotype 1.10, which was derived from a patient with active SLE and antiphospholipid syndrome, was found more frequently among patients with PAPS (10.5%, 10.5% and 22.2% in MG, SLE and PAPS, respectively) than the idiotype H3, which was derived from a human hybridoma monoclonal aCL generated from a healthy subject immunized with tetanus and diphtheria. The latter idiotype was detected in 8.7%, 6.5% and 11.7% of patients with MG, SLE and PAPS, respectively. Incidental findings in this study include a high prevalence of aCL among patients with MG (23%) and a high prevalence of anti-dsDNA antibodies, detected only by a sensitive enzyme-linked immunosorbent assay, among patients with PAPS. Our results indicate that idiotypic diversity exists among aCL derived from different sources. Some of these cross-reactive idiotypes may be more pathogenic than others.

Analysis of antibody reactivity in the sera of 42 patients with paraproteinaemia

The clinical expression of disease in patients with conditions in which autoimmunity is thought to contribute to the pathogenesis of disease is the result of an unfortunate combination of predisposing and environmental factors. The presence of autoantibodies showing a variety of antigen specificities in sera from many of these patients has been closely correlated with particular spectra of organ involvement or tissue destruction. Their precise role in the disease process is as yet unclear. Sera from patients with paraproteinaemia also often contain autoantibodies to a variety of cell components, although symptoms of autoimmune disease are rarely found in this group of individuals. In this study of 42 sera from patients with paraproteinaemia we have confirmed the presence of autoantibodies in 33% (13/42) of samples. Amongst the autoantibodies detected were those to human neutrophils (3), U1RNP (8) and cardiolipin (4). In five sera, the immunoglobulin class of autoantibody did not correlate with that of the monoclonal band. This study extends previous reports of the repertoire of autoantibodies present in sera from patients with paraproteinaemia.

Autoantibodies in neoplasia. An unresolved enigma

One hundred sixty-four sera samples of patients with malignant diseases were analyzed for the presence of autoantibodies to ssDNA, dsDNA, poly(I), Poly(G), cardiolipin, histones, RNP, Sm, Ro(SSA), and La (SSB). No distinction could be made between these patients and a comparative group composed of age-adjusted healthy subjects when measuring antibody levels to these autoantigens by the ELISA technique. This finding remained valid after further subgrouping of the patients according to age, sex, and histologic origin of the tumor. The authors conclude that in contrast to the known clinical coexistence of neoplasia in autoimmune states, there is no increased incidence of antinuclear autoantibodies in malignant conditions.

The importance of the pathogenic 16/6 idiotype in the induction of SLE in naive mice

We have previously demonstrated the pathogenicity of the common anti-DNA idiotype designated 16/6 Id. Immunization of naive mice with the 16/6 Id induced SLE-like disease characterized by serological (e.g. anti-dsDNA and anti-Sm auto-antibodies), clinical (increased ESR, leucopenia and proteinuria), and pathological (16/6 Id deposition in kidneys) parameters. To elucidate further the role of the 16/6 Id in SLE induction the following studies were carried out: BALB/c mice were immunized with SA-1, a human anti-DNA monoclonal antibody carrying the 16/6 Id; TB-68, a mouse monoclonal anti-tuberculosis (TB) glycolipid, which binds dsDNA and carries the 16/6 Id; TB-72, a mouse monoclonal anti-TB glycolipid that binds DNA and does not harbour the 16/6 Id; and 4B4, a human anti-Sm antibody that carries the 16/6 Id. SLE was induced in BALB/c mice only when immunized with SA-1, TB-68, and 4B4, namely antibodies with diverse binding capacities albeit having the 16/6 Id. Our studies further support previous evidence on the pathogenic role attributed to the 16/6 Id in SLE, and suggest that SLE is most probably an idiotype-induced disease.

Down-regulation of autoantibody levels of cyclosporine and bromocriptine treatment in patients with uveitis

The administration of cyclosporine A, cyclosporine A plus bromocriptine, or bromocriptine results in down-regulation of antinuclear autoantibody levels in the sera of patients with uveitis. Decreased levels of autoantibodies against DNA, histones, cardiolipin, RNP, Sm, Ro (SS-A), and La (SS-B) were detected in the sera of patients with uveitis receiving cyclosporine A or cyclosporine A plus bromocriptine following 3 months of treatment. In contrast to the decreased antibody titers obtained following the treatment, the total immunoglobulin levels remained within the normal range. The results indicate that cyclosporine may affect B cell function, thereby yielding the observed decrease in autoantibody levels. This phenomenon might have clinical importance as a serological indicator of the efficiency of the patients to respond to the drug.

Analysis of autoantibody reactivity and common idiotype PR4 expression of myeloma proteins

Sera from 75 patients with monoclonal gammopathies and with no clinical evidence of autoimmune disease have been screened for a wide range of autoreactivity including binding to DNA, cardiolipin, extractable nuclear antigen (ENA), rheumatoid factor activity and the presence of the common anti-DNA antibody idiotype PR4. The sera of 17/75 (23%) patients possessed autoreactivity: six were positive for anti-DNA activity, two had anticardiolipin activity and the PR4 ID was found in two sera (both of which possessed anti-DNA activity). Antibodies to ENA were found in one serum (anti-Ro) and anti-organ-specific antibodies in five. Using iso-electric focusing and immunoblotting we have shown that the PR4 ID and DNA binding activity are carried on the paraprotein and not on some other serum constituent. The IgG subclass distribution of 55 IgG paraproteins has also been investigated. The majority of IgG paraproteins belong to IgG1 subclass (55%), with the others, being IgG2 (4%), IgG3 (9%) and IgG4 (27%). In this study we have shown that sera from myeloma patients frequently possess autoreactivity, and that in many cases this can be attributed to the paraprotein.

Autoantibodies to histones and their subfractions in chronic liver diseases

Sera of 78 patients with different chronic liver diseases were examined for the presence of anti-histone activity using an enzyme-linked immunosorbent assay. Eighteen patients had primary biliary cirrhosis (PBC), 20 had chronic active hepatitis, and 40 had cirrhosis. Anti-histone antibodies were detected in 34 patients (43.6%), distributed among all liver disease entities studied. When antibodies of specific isotypes (IgG, IgM, and IgA) were measured, even higher frequencies were noted--50% for IgG and 53.8% for IgA. Antibodies to histone subfractions H1, H2a, H2b, H3, and H4 were also observed in all liver disorders investigated (in 22-32% of patients)--H1 and H3 being the prominent fractions involved. Of the various disease entities examined PBC was the one disclosing the highest frequency of anti-histone antibodies.

DNA-anti-DNA complexes account for part of the antihistone activity found in patients with systemic lupus erythematosus

We examined the effect of DNase treatment of sera with antihistone activity. In non-systemic lupus erythematosus (SLE) sera, antihistone levels remained unmodified, but a significant decrease was observed in 7 of 11 SLE sera with anti-DNA antibodies. This was accompanied in some by an increase in anti-DNA levels. We therefore considered that DNA-anti-DNA complexes were being detected, as part of the antihistone activity in SLE patients, by binding of the complexes through their DNA to the histones used in the assay. This was confirmed by demonstrating that DNA-anti-DNA complexes formed in vitro, and by studies performed with monoclonal antibodies with affinity to double-stranded DNA and/or histones.

Antinuclear and related autoantibodies in sera of healthy subjects with IgA deficiency

The sera of 49 healthy IgA-deficient (SIgAD) subjects were evaluated for the presence of autoantibodies directed against 10 different nuclear and cytoskeletal antigens, as well as for the presence of the common lupus anti-DNA idiotype (16/6 Id). Twenty-nine sera were from IgG subclass-deficient subjects (4 = IgG2, 25 = IgG3), and 25 from normal healthy subjects, used as controls. The incidence of antinuclear but not anti-cytoskeletal antibodies were found to be significantly greater in the SIgAD group, as compared to the IgG-deficient subjects and the normal controls. Overall, 39% of SIgAD sera demonstrated polyreactivity, namely reactivity against more than one nuclear antigen. The incidence of specific antibody detection ranged from 37% against cardiolipin to 12% against RNP in the IgA-deficient group, albeit not with statistical significance in all cases when compared to the control group. Isotype evaluation of the antinuclear and related antibodies in the SIgAD group showed a greater tendency towards IgG. This increased incidence of autoantibody production in SIgAD may preceed the development of an overt autoimmune disease in the future.

Antibody specificity of the human monoclonal immunoglobulins: the elusive target antigen

Human monoclonal immunoglobulins (HMIGs) are encountered in different clinical conditions mainly including (auto)immune disorders, immunodeficiencies and B-cell malignancies. However, in some cases no associated-disease is evidenced and they are considered as "idiopathic". Their incidence increases with age. The factors involved in the emergence and regulation of the growth and differentiation of B-cell clones secreting HMIGs are unknown but might implicate T-cell dysfunction. One approach to elucidate the origin of such B-cell clones is to identify the putative target antigen. For this reason, we have reviewed the antibody (Ab) specificity of 8439 HMIGs described in the literature, the data coming from 24 systematic screenings. Very few HMIGs present anti-hapten activity (1%) or specificity for foreign antigens (0.3%). On the other hand, the data quoted strongly document an auto-Ab (Ab1 type) activity in a large percentage of the HMIGs, mainly of the IgM type (at least greater than 30%), with properties similar to those of naturally occurring auto-Abs. Furthermore, there is some evidence that HMIGs may express anti-idiotypic activity (Ab2) to human (auto)-Abs. Finally, many of the HMIGs which are devoid of detectable auto-Ab activity (i.e., mainly IgG, IgA) share cross-reactive idiotypes with natural auto-Abs. It may be speculated that some of these HMIGs actually represent either Ab of the Ab3 type i.e., anti-anti-idiotypic Ab to auto-Abs or Ab which have varied sufficiently to loose auto-or-foreign-antigen-binding activity but maintaining idiotype. As a whole, these data demonstrate that many HMIGs are the secretory products of the auto-reactive B-cell clones which produce natural auto-Abs (including anti-idiotypic and anti-anti-idiotypic Abs) and which are characterized by a very high degree of idiotypic connection. Since HMIGs arise from such clones, it may be postulated that the emergence of HMIGs might be due to a dysfunction of the system that normally regulates such an Ab production.

Naturally-occurring tumor-reactive autoantibodies: a monoclonal antibody from normal mice reacts with tumor cells and with DNA

A natural IgM monoclonal antibody, 1.67, was generated from apparently healthy unstimulated BALB/c mice. This antibody reacted with L5178Y murine T cell lymphoma, with human Raji cells, and with several normal cells. Further analysis of its ligand binding capacity disclosed strong binding to single-stranded DNA (ssDNA). However, this naturally-occurring monoclonal antibody binds to different epitopes on cell membranes and on DNA than another anti-DNA monoclonal antibody (18/103/1) from human origin. This conclusion was based on competition assays. Furthermore, NOA 1.67 lacks the 16/6 idiotype expressed on the 18/103/1 antibody. The 16/6 idiotype is shared by human and mouse lupus monoclonal autoantibodies that bind simultaneously to lymphoid cells and DNA. This is a first report on a natural autoantibody that binds to malignant and to normal cell membrane(s) as well as to ssDNA. It may have regulatory functions controlling malignancy and or autoimmunity.

Increased presence of common systemic lupus erythematosus (SLE) anti-DNA idiotypes (16/6 Id, 32/15 Id) is induced by procainamide

Sixty-seven patients on treatment with procainamide were examined for the presence of two common idiotypes of anti-DNA antibodies (16/6 Id and 32/15 Id). These idiotypes have been shown previously to have clinical relevance in patients with systemic lupus erythematosus (SLE). An enzyme-linked immunosorbent assay (ELISA) with rabbit anti-Id antibodies revealed increased concentrations of the 16/6 Id and 32/15 Id in 25 (37%) and 16 (24%) patients, respectively. Five of eight patients with drug-induced lupus had elevated titers of both idiotypes. A high correlation (R = 0.56, P less than 0.001 for 16/6 Id) was found between Id levels and anti-single-stranded DNA (ssDNA) antibody titers and between 16/6 Id titers and antihistone antibodies (IgG, R = 0.43; IgM, R = 0.25). It seems that procainamide, a component known to be associated with drug-induced lupus, may induce an increased production of common anti-DNA idiotypes in apparently normal subjects.