Possible mechanism for down-regulation of autoantibody production by auto-anti-idiotype

Increased proliferation of blood mononuclear cells after plasmapheresis treatment of patients with demyelinating disease

Induction of lymphocytic proliferation has been postulated to be a mechanism whereby plasmapheresis may enhance the action of cytotoxic immunosuppressive drugs. This study found increased spontaneous proliferation of peripheral blood mononuclear cells following intensive plasmapheresis treatment of patients with multiple sclerosis (MS) or Guillain-Barré syndrome (GBS). The increased proliferative response was reduced below baseline in four of six MS patients who received subsequent immunoglobulin intravenous (IGIV) and pulsed cyclophosphamide therapy, but not in three MS patients receiving IGIV alone. In five GBS patients with low baseline proliferation, proliferation also increased after plasmapheresis. High baseline proliferation found in three GBS patients may have reflected antecedent infection, since it fell during plasmapheresis in the two patients in whom it was measured. Plasmapheresis could possibly augment the effectiveness of cytotoxic drugs in controlling autoimmunity by inducing lymphocytes to proliferate, thereby making them more susceptible to drug action.

Alteration of idiotypic connectivity in prenatally tolerized neonatal mice

Prenatal tolerization with trinitrobenzenesulphonic acid (TNBS) leads to expansion of trinitrophenyl (TNP)-specific B cells, the majority of which become refractory to stimulation during postnatal development. One possible explanation could be that they belong to the repertoire of naturally activated B cells which are limited in expansion after antigenic stimulation due to a high degree of idiotypic connectivity. To evaluate this hypothesis, 59 thymus- and 490 spleen-derived B-cell hybridomas from 6-day-old prenatally untreated and prenatally TNBS-treated mice were tested for reactivity against 33 arbitrarily chosen clones derived from the same fusions, 17 being derived from control and 16 from tolerized litters. Two major points could be deduced: (1) Idiotypic connectivity, including connectivity of TNP- and anti-TNP-reactive monoclonal antibodies (MoAb), was maintained after prenatal tolerization. This accounted for thymus- and spleen-derived MoAb. (2) Only TNP- and anti-TNP-reactive MoAb derived from prenatally untreated and prenatally tolerized mice displayed significantly distinct idiotypic profiles. Differences were pronounced, especially with thymus-derived MoAb. Thus, TNP-specific B cells in prenatally tolerized newborns do not behave like B cells of adult mice stimulated by external antigen, but rather like a part of the naturally activated, idiotypically connected B-cell repertoire of the newborn. This could explain B-cell unresponsiveness at older age as a consequence--at least partly--of their high idiotypic connectivity.

Recognition of idiotypic structures in the thymus

During the passage through the thymus, T cells are selected which recognize self major histocompatibility complex (MHC) antigens with low avidity. Whether the T-cell repertoire for recognition of altered self is also built up intrathymically or in the periphery, and whether it is determined exclusively by external antigens or is shaped by the internal environment is still a matter of debate. This question was addressed by analysing the responsiveness of thymocytes during post-natal development towards a nominal antigen [trinitrophenyl (TNP)] and an anti-TNP monoclonal antibody (Sp6), which carries a recurrent idiotype. During the first weeks of life, in vitro cultures of thymocytes proliferated strongly in the absence of nominal antigen. Proliferation rates were not increased by the addition of nominal antigen [TNP-ovalbumin (OA)], but a significant increase was noted in the presence of Sp6, thymocytes recognizing the processed immunoglobulin. After in vivo stimulation with TNP conjugates, 'antigen-specific' clones could also be detected in the thymus, the frequency of clones proliferating in response to Sp6 being further augmented. With increasing age, the proliferative capacity of thymocytes from unstimulated and antigenically stimulated mice decreased significantly. Responsiveness of spleen cells (SC) differed in some respects. The response towards Sp6 decreased with age, while antigen-specific clones were detected at increasing frequencies during post-natal development. Furthermore, after antigenic stimulation, the frequency solely of antigen-specific, but not of Sp6-specific clones was increased. Thus, it appears that the T-cell repertoire is shaped already during the intrathymic passage, being influenced primarily by the B-cell repertoire and modulated further by external antigen.

Postnatal B cell development: influence of trinitrobenzenesulfonic acid treatment during pregnancy

Prenatal treatment with a reactive hapten may be well suited for analyzing the establishment of self tolerance because the hapten binds ubiquitously to proteins and cells and persists for a long period in the developing organism. Based on this consideration, pregnant BALB/c mice were treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS), searching for differences in 2,4,6-trinitrophenyl (TNP) responsiveness in their offspring as compared to litters of untreated mice. The frequency of TNP-specific T-independent B cells of litters from TNBS-treated mothers was very low at birth and remained below 10% of controls until the age of 42 days. On the contrary, in 8-day-old prenatally TNBS-treated litters, the frequency of TNP-specific T-dependent B cells was higher than in controls. Expansion of TNP-specific B cells after antigenic stimulation of control mice started at the age of 3-4 weeks and expansion rates increased with age, while in prenatally TNBS-treated mice, significant expansion rates were seen at the age of 2 weeks only. Yet, after restimulation with TNP-lipopolysaccharide or with a TNP-anti-TNP conjugate, but not after restimulation with TNP-ovalbumin, similar numbers of plaque-forming cells (PFC) were observed with spleen cells of prenatally untreated and TNBS-treated mice, the latter revealing an exceptional predominance of IgG PFC. Thus, TNP-specific B cells were not deleted, but prenatal TNBS treatment resulted in an altered composition of TNP-specific B cell subpopulations, their regulation differing qualitatively from the one observed in prenatally untreated mice.

The start of an autoimmune disease: idiotypic network during early progression of myasthenia gravis

Anti-acetylcholine-receptor antibodies of IgG and IgM classes and antiidiotypic antibodies were determined in patients with myasthenia gravis at various times after the start of the disease. Patients with a disease duration of less than one year had a higher prevalence of antiidiotypic antibodies (31/32) than patients who had had the disease for more than 5 years (49/79), and the concentration of antiidiotypic antibodies was also higher in patients with early disease (p less than 0.005). The concentrations of antiidiotypic antibodies decreased during progression of the disease concomittant with an increase in IgG anti-receptor antibodies. A change from IgM to IgG anti-receptor antibody production was also found. In two patients, who developed myasthenia after bone-marrow grafting and who were followed before start of disease, antiidiotypic antibodies appeared before anti-receptor antibodies and before symptoms of myasthenia were present. The high prevalence and concentration of antiidiotypic antibodies in early disease indicate that development and expression of antiidiotypic antibodies are important in early myasthenia gravis.

Prevention of experimental autoimmune uveoretinitis by active immunization with autoantigen-specific monoclonal antibodies

Preimmunization of Lewis rats with anti-S antigen (S-Ag) monoclonal antibodies (mAb) led to protection against experimental autoimmune uveoretinitis (EAU) induced by this retinal autoantigen. High titers of anti-idiotypic (anti-Id) antibodies were raised against three mouse mAb, S2D2 (IgG2b), S6H8 (IgG2a) and S7D6 (IgG1), directed at S-Ag. An almost complete prevention was observed in S2D2 mAb-immunized animals while a partial protection was achieved with S6H8 and S7D6 mAb. No detectable anti-Id antibody nor disease prevention was observed in rats immunized with the mAb S9E2 (IgG2a) which only recognizes bovine and sheep S-Ag, or with control mAb of the same isotypes irrelevant to S-Ag. The mAb treatment did not modify the level of the whole polyclonal antibody response to S-Ag. These results suggest an important role in the pathogenesis of EAU for the epitopes recognized by S2D2-S6H8 and S7D6 in the S-Ag molecule. The success of anti-Id immunization for autoimmune disease suppression may depend on the identification of relevant epitopes.

Anti-idiotypic antibodies to anti-DR in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) sera were evaluated for anti-idiotypic (anti-id) antibodies to HLA-DR antigens (anti-DR) using an ELISA method with murine monoclonal anti-DR antibody-coated microtiter plates incubated serially with either normal or RA sera and peroxidase-conjugated goat anti-human IgG (Fc specific). Specificity was examined using other monoclonal antibodies including anti-Leu 3a, OKM5, OKT8, anti-cytochrome c, and anti-breast tumor antigen. Significant binding of 11/33 (33%) RA to anti-DR was found compared with 0/44 normals (P less than 0.001). Two groups were identified: RA sera reacting with anti-DR and anti-Leu 3a and sera which did not bind to anti-DR but bound to irrelevant monoclonal antibodies. Anti-DR reactivity was differentiated from anti-Leu 3a by competitive inhibition studies. Binding of whole sera and IgG from RA patients to anti-DR was significantly inhibited by DR+ cell extract. The same extract was not inhibitory after selective removal of DR antigen by adsorption on an anti-DR-Sepharose column. These data suggest that anti-id antibodies are directed against the antigen-binding site of id. We conclude that some RA patients have anti-id antibodies potentially involved in immunoregulation of anti-DR antibodies.

The origin of autoantibodies

Autoimmune diseases are characterized by the appearance of autoantibodies (autoAb) which may participate in their pathogenesis, but autoAb have also been found in normals with a variety of other conditions. The production of hybridomas from lymphocytes of unimmunized normal mice and healthy humans and analysis of the monoclonal autoAb (m-autoAb) obtained, showed that many had polyspecific autoAb reactivity, binding to many seemingly unrelated self-antigens, or to several organs. Most m-autoAb were of the IgM class and shared a common cross-reactive idiotype (CRI). Low levels of Ab with similar binding pattern and idiotype are continuously represented in the serum of mice and humans who have no evidence of autoimmune or other disease. Very similar Ab appear in autoimmune diseases. Studies of m-autoAb derived from lupus-prone mice and from patients with systemic lupus erythematosus (SLE) and other autoimmune diseases also revealed polyspecific binding, IgM isotype and CRI. Moreover, these CRI, which were almost identical with the idiotypes of natural autoAb in normals, may identify a group of pathogenic Ab in the lupus mice and SLE patients. Since the data clearly suggest that lymphocytes that make autoAb are common and are part of the normal B cell repertoire coded by widely dispersed germline genes, there remain the basic problems of the function of these autoAb in health, as well as the question of their regulation and activation in vivo. Several postulated functions and immunoregulatory mechanisms are discussed and the possible role of certain factors, especially viruses, in enhancing autoAb production and autoimmunity, is assessed.

Modulation of murine coxsackievirus-induced myocarditis utilizing anti-idiotypes

Pre-treatment of syngeneic mice with polyclonal populations of Protein-A separated anti-idiotypic antibodies prepared against anti-CVB3 viral idiotypes resulted in reduction of inflammatory myocarditis in virus-challenged mice. Cellular immunity as assessed by cell-migration-inhibition resulted in specific cell-mediated sensitivity against anti-Ids (CVB3) as well as viral preparations. Animals pre-treated with anti-idiotypic preparations developed an anamnestic anti-viral antibody response, with antibodies capable of specifically binding CVB3 virus antigen in an ELISA assay; but without CVB3 viral neutralizing capability. Adoptive transfer of limited numbers of syngeneic anti-Id immunized lymphoid cell populations failed to alter the course of inflammatory myocarditis in CVB3 virus-challenged animals. Cellular binding studies utilizing anti-Ids suggested increased, but nonspecific binding of anti-Ids to lymphoid and myocyte populations in CVB3 infected animals. The data suggest an immunomodulatory role of idiotype-anti-idiotype interactions in the development of myocarditis.

Suppressor cell function and anti-DNA antibody idiotypes in the serum of SLE patients and their first-degree relatives

Sixteen-six (16/6) is a major cross-reactive idiotype of monoclonal anti-DNA antibodies, which was derived from the fusion of lymphocytes of a patient with systemic lupus erythematosus (SLE). Antibodies with the 16/6 idiotype (16/6 Id) are increased in the sera of patients with SLE and deposited in their gomeruli and skin. Since stimulated lymphocytes from healthy persons have the capacity to produce 16/6 Id, the mechanisms controlling its expression in health and their possible failure in SLE are of considerable interest. A defect in suppressor cell function was found in a high proportion of patients with SLE and in some of their first-degree relatives. Suppressor cell function in 15 SLE patients and in 53 relatives was compared with the level of 16/6 Id as well as with immunoglobulin levels and anti-DNA antibodies. Ten of 15 SLE patients and 26 of 53 first-degree relatives had increased serum 16/6 levels, which was found in only 1 of 35 healthy controls and household members. Of the 10 SLE patients with increased 16/6, six had a suppressor cell defect (P less than 0.1). Among the 26 first-degree relatives with elevated 16/6 Id levels, 12 had associated suppressor defect and in only two cases was a suppressor cell defect unaccompanied by increased 16/6 (P less than 0.005). For the group of 18 patients and relatives showing concomitant suppressor cell defect and increased 16/6, a correlation was found between the severity of the suppressor cell defect and the level of 16/6 Id in the serum. The increased 16/6 in the relatives was not associated with hypergammaglobulinemia or with measurable anti-DNA activity in the serum. We conclude that the suppressor cell defect in relatives of SLE patients is often associated with increased expression of antibodies with the 16/6 idiotype. However, additional mechanisms are involved in the regulation of 16/6 Id and the development of clinical SLE, since increased 16/6 was commonly found in the presence of a normal suppressor T-cell function.

Age-related increase of focal lymphocytic infiltration in the human submandibular glands

Histopathological studies were made on the submandibular glands, obtained from 207 autopsy cases of patients, ranging in age from 40-98 years who had not had collagen diseases. Focal lymphocytic infiltration of the submandibular glands was more frequently seen in the cases of patients over 70 years (80.3%) than in those of under 70 years (53.8%). Generally, the incidence of focal lymphocytic infiltration showed a trend to gradual increase with age. Immunohistochemically, a predominance of T cells (60-80%) was found in submandibular lesions with the majority (60-70%) belonging to the Leu 3a+ subset (Helper/Inducer) and with less than 20% belonging to the Leu 2a+ subset (Cytotoxic/Suppressor). The percentage of Leu 2a+ subset was found to increase in the lesion of the periacinar area, and the acinar parenchyma appeared gradually to be damaged by the infiltrating lymphocytes. The findings in the present study suggest that focal lymphocytic infiltration in submandibular glands is a focal sign of immunological disorder, based on the autoimmunity associated with aging.