Inhibition of autoantibody production in experimental SLE by pre-immunization with DNA

Experimental SLE can be induced in susceptible mice by their immunization with the human monoclonal anti-DNA antibody that bears a major idiotype-16/6 Id. The SLE afflicted mice produce a variety of autoantibodies including anti-DNA antibodies. It was of interest to find out the effect of DNA on the induction of the experimental disease. To this end, mice were immunized with combinations of 16/6 Id and DNA. The results indicated that whereas mice primed with 16/6 Id developed high titers of antibodies to the 16/6 Id and a variety of autoantibodies typical to the experimental SLE, preimmunization of mice with ssDNA led to a reduction in the 16/6 Id specific antibodies and in the autoantibody titers. No significant differences could be detected in the clinical manifestations which are present in the mice with experimental disease (increased erythrocyte sedimentation rate, leukopenia, proteinuria and glomerular immune complex deposition) in all mice immunized with 16/6 Id including those pretreated with DNA. Thus, no direct correlation exists between the autoantibody levels and the clinical pathology, and probably other factors are involved in the development of the experimental disease.

The role of the 16/6 idiotype network in the induction and manifestations of systemic lupus erythematosus

Experimental systemic lupus erythematosus (SLE) has been induced in mice by immunization with either a human anti-DNA mAb bearing a common idiotype (Id) designated 16/6 Id (antibody 1, Ab1) or with a murine anti-16/6 Id mAb (Ab2). In the present study a murine mAb (5G12-4, Ab3) that bears the 16/6 Id and binds to DNA was produced and was found to bind rabbit anti-16/6 Id sera and murine anti-16/6 Id mAb similarly to the human mAb 16/6 Id (Ab1). Moreover, mAb 5G12-4 was shown to share T cell epitopes with the human 16/6 Id mAb, since lymph node cells of mice immunized with the mAb 5G12-4 proliferated significantly to the human 16/6 mAb and vice versa. Following immunization of mice with the murine mAb bearing the 16/6 Id, antibodies to dsDNA, ssDNA, 16/6 Id, anti-16/6 Id, and to HeLa nuclear extract proteins were detected, similarly to those observed previously upon immunization with Ab1 or Ab2. Six months following the immunization, the mice exhibited leukopenia, increased erythrocyte sedimentation rates, and proteinuria. Examination of the kidneys of the mice disclosed immune complex deposits, thickening of the Bowman's capsule and glomerular necrosis. These results show the importance of the 16/6 Id network in the induction and progression of SLE in mice.

Systemic lupus erythematosus-related autoantibody production in mice is determined by bone marrow-derived cells

Experimental systemic lupus erythematosus (SLE) can be induced in mice by immunization with either a human monoclonal anti-DNA antibody bearing the 16/6 idiotype (16/6 Id) or with a mouse monoclonal anti-idiotypic antibody specific for the 16/6 Id. Susceptibility to the induction of experimental SLE is genetically determined but is not linked to the MHC. In the present study we tested the susceptibility of BM chimeras of different donor-host combinations to the induction of SLE and found that high levels of anti-16/6 Id and anti-ssDNA antibodies were induced in BALB/c-->C57BL/6, BALB/c-->BALB/c and normal BALB/c mice as opposed to C57BL/6-->BALB/c chimeras and normal C57BL/6 mice. The low levels of the anti-16/6 Id and anti-ssDNA antibodies produced by C57BL/6-->BALB/c chimeras immunized with the 16/6 fully allogeneic BMT as such chimeras were shown to produce high levels of antibodies to a T cell-dependent antigen (the synthetic polypeptide (Phe,G)-A--L). These results demonstrate that the production of SLE-related autoantibodies is controlled by donor-type BM derived cells and not by host-type cells in the thymic stroma.

Effect of macrophage infection by Leishmania on the proliferation of an antigen-specific T-cell line, TPB1, to a non-parasite antigen

The ability of Leishmania mexicana amazonensis to inhibit antigen specific T-cell proliferation against a non-parasite polypeptide antigen, poly(LTyr, LGlu)-poly(DLAla)--poly(LLys), was examined. Infection of mouse peritoneal macrophages by promastigotes blocked the proliferation of the T-cell line, TPB1. This effect was correlated with the level of parasite infection, and the timing of macrophage infection and antigen addition. Peritoneal macrophages from both BALB/b and C57BL/6 mice showed reduced ability to serve as antigen presenting cells.

Inhibition of T-cell reactivity to myasthenogenic epitopes of the human acetylcholine receptor by synthetic analogs

The synthetic peptides p195-212 and p259-271, representing amino acids 195-212 and 259-271 of the alpha subunit of the human acetylcholine receptor, preferentially stimulate T cells of patients with myasthenia gravis and are immunodominant T-cell epitopes in SJL and BALB/c mice, respectively. We designed and synthesized analogs of these peptides that contain single amino acid substitutions. An analog of peptide p195-212, no. 455 (Met-207-->Ala), was capable of inhibiting up to 100% of the proliferative responses of a p195-212-specific T-cell line originating from the high-responder strain SJL. Similarly, an analog of p259-271, no. 306 (Glu-262-->Lys), was capable of inhibiting up to 93% of the proliferative responses of the p259-271-specific T-cell line originating from high-responder BALB/c mice. Analog 306 also inhibited up to 43% of the proliferative responses of p259-271-primed lymph node cells in an in vitro proliferation assay. To test the in vivo inhibitory activity of the analogs, mice were primed with the myasthenogenic peptides in complete Freund's adjuvant concomitant with administration of the analogs in aqueous solution. Administration of analogs 455 and 306 led to decreased proliferative responses of up to 70% by peptide p199-212-primed lymph node cells and up to 85% by peptide p259-271-primed lymph node cells. Similar results were obtained whether the analogs were administered i.v. or i.p. Thus, these analogs are good candidates for specific immunomodulatory therapy for patients with myasthenia gravis.

Anti-cardiolipin antibodies induce pregnancy failure by impairing embryonic implantation

The antiphospholipid syndrome is characterized by thrombocytopenia, thrombosis, and recurrent fetal loss in association with anti-cardiolipin antibodies (ACAs) or lupus anti-coagulants. However, the causal role of these antibodies in the disease and the mechanisms by which the ACA may induce the syndrome are not clear. Recently, we have established an experimental mouse antiphospholipid syndrome induced by the mouse IgM monoclonal ACA designated 2C4C2. In the present study, we focused on the effects of immunization with the monoclonal ACA 2C4C2 on the outcome of pregnancies in BALB/c female mice. Four weeks after active immunization with the monoclonal ACA, a severe gestational failure with low pregnancy rates, low number of fetuses, and a high rate of resorptions was observed. Moreover, embryos obtained from the ACA-immunized females on day 3.5 of pregnancy were severely impaired, demonstrating developmental delay and abnormal morphology. These abnormal embryos failed also to develop in an in vitro implantation model. Furthermore, specific binding of the 2C4C2 ACA to the trophectoderm cell lineage of in vitro implanting normal embryos was observed. Thus, our studies demonstrate that the severe ACA-induced gestational failure results from an impairment of implantation and suggest that the ACA may react directly with the preimplantation embryos.

Resistance of MHC class I-deficient mice to experimental systemic lupus erythematosus

Experimental systemic lupus erythematosus (SLE) can be induced in mice by immunization with a human monoclonal antibody to DNA that bears a common idiotype (16/6Id). These mice generate antibodies to 16/6Id, antibodies to DNA, and antibodies directed against nuclear antigens. Subsequently, manifestations of SLE develop, including leukopenia, proteinuria, and immune complex deposits in the kidney. In contrast, after immunization with 16/6Id, mice lacking major histocompatibility complex (MHC) class I molecules generated antibodies to 16/6Id but did not generate antibodies to DNA or to nuclear antigen. Furthermore, they did not develop any of the above clinical manifestations. These results reveal an unexpected function of MHC class I in the induction of autoimmune SLE.

Variable region sequences of autoantibodies from mice with experimental systemic lupus erythematosus

We have sequenced nine monoclonal antibodies (mAb) derived from C3H.SW mice in which experimental systemic lupus erythematosus (SLE) was induced. The hybridomas were selected for binding to DNA or to HeLa nuclear extract (NE). Three mAb were found to bind DNA, and are shown to exhibit sequence characteristics of pathogenic anti-DNA antibodies. One, mAb 2C4C2, is shown to use a heavy chain V region gene (VH) identical to the VH of anti-DNA mAb isolated from other lupus-prone mice, namely (NZB x NZW)F1. The light chain V region gene (VL) of mAb 2C4C2 is 98% homologous to the VL of another anti-DNA mAb, also isolated from (NZB x NZW)F1 mice. The other two anti-DNA mAb, 5G12-4 and 5G12-6, share 93% of their VH sequences with that of mAb 2C4C2. Six mAb bound proteins of HeLa NE. Four of these six antibodies were found to use the VH124 VH and V-L7 VL. The nine mAb use a total of five VH and four VL germ-line genes, demonstrating that the autoantibodies induced in mice with experimental SLE do not originate from one B cell clone. Three of these nine VH and VL were identical in sequence to germ-line genes, while at least three others had somatic mutations. The latter suggests that the above autoantibodies arise in mice by both usage of existing (pre-immune) B cells, and through an antigen-driven process. Furthermore, it appears that autoantibodies found in mice with experimental SLE use genetic elements similar to those used by mAb that were isolated from mouse strains which develop lupus spontaneously.

Monoclonal anticardiolipin antibodies derived from mice with experimental lupus erythematosus: characterization and the induction of a secondary antiphospholipid syndrome

The primary antiphospholipid syndrome and the antiphospholipid syndrome in systemic lupus erythematosus (SLE) patients (defined as secondary antiphospholipid syndrome) are characterized by the presence of anticardiolipin antibodies, thrombosis, thrombocytopenia, and recurrent fetal loss. To determine the role of anticardiolipin antibodies in the pathogenesis of antiphospholipid syndrome, monoclonal anticardiolipin antibodies were derived from mice in which experimental lupus was induced by a murine monoclonal anti-16/6 Id antibody. Two murine monoclonal anticardiolipin antibodies (2C4C2, 2C4D1) were generated and characterized. The 2C4C2, but not the 2C4D1, monoclonal antibody demonstrated remarkable lupus anticoagulant activity. Furthermore, these murine anticardiolipin monoclonal antibodies appear to recognize antigenic epitopes similar to those recognized by anticardiolipin antibodies found in sera of SLE patients. The monoclonal anticardiolipin antibody 2C4C2 was injected into naive female mice. Following immunization, the mice developed high titers of autoantibodies reacting with cardiolipin, DNA, nuclear extract, 16/6 and anti-16/6 Id, and anticardiolipin antibodies. As early as 8 weeks after immunization these mice exhibited significant leukopenia, thrombocytopenia, and proteinuria with immune complex glomerulonephritis. Moreover, mating of 2C4C2-injected mice with allogenic males resulted in low pregnancy rates and a low number of fetuses with a high percentage of fetal loss. These studies provide a new experimental model for secondary antiphospholipid syndrome demonstrating the role of anticardiolipin antibodies in the pathogenesis of this syndrome.

Ia-antigen-T-cell interactions for a thymus-independent antigen composed of D amino acids

Synthetic polypeptide antigens of L amino acids, although bearing repeating sequences, are thymus-dependent (L-TD), whereas the same polymers composed of D amino acids are thymus-independent (D-TI), probably due to a slower rate of metabolism. Yet we found that lymph-node cells of BALB/c mice immunized with D-TI proliferate in response to it in vitro. To follow T-cell activation by D-TI, we established T-cell hybridomas to D-TI and to its analog composed of L isomers, L-TD, for comparison. The T-cell hybridomas express membrane alpha/beta T-cell receptors and secrete interleukin 2 upon stimulation with the respective antigen. In addition, D-TI-specific hybridomas are stimulated, to a lesser extent, by the L-TD antigen, whereas only some L-TD-specific hybridomas recognize D-TI. Moreover, biotinylated analogs of D-TI and L-TD bind to splenic antigen-presenting cells (APCs) from BALB/c mice. Binding is inhibited by an excess of nonbiotinylated L-TD, and by an excess of a peptide comprising residues 259-271 of the human acetylcholine receptor alpha subunit, which binds to I-Ad and I-Ed molecules without prior processing. Analysis of APC lysates following incubation of the APCs with biotinylated D-TI and L-TD reveals that the biotinylated antigen moiety is associated with Ia molecules. D-TI and L-TD bind to Ia molecules on intact APCs with similar KD values, 5 x 10(-8) M and 3 x 10(-8) M, respectively. However, D-TI has faster kinetics of binding than L-TD, probably due to different processing requirements. Hence, we have demonstrated a major histocompatibility complex class II-mediated T-cell response to a thymus-independent antigen.

Neonatal lupus erythematosus in offspring of mothers with experimental systemic lupus erythematosus

Neonatal lupus erythematosus (NLE) syndrome is a result of the transfer of autoantibodies produced by the mother, across the placenta, to the fetus. NLE is characterized by a transient dermatitis, a variety of systemic and hematological abnormalities, and isolated cases of congenital heart block. The latter has been reported to be due to the presence of autoantibodies specific to La (SS-B) and/or Ro (SS-A). As female mice with experimental SLE, induced by immunization with the monoclonal anti-DNA 16/6 Id, produce a variety of autoantibodies including anti-Ro and anti-La antibodies, we examined the relevance of NLE in the murine system. Offspring of SLE-afflicted BALB/c mothers possessed antibody titers to the 16/6 Id, ssDNA, and nuclear extract, which gradually declined until reduced to normal levels by day 60 after delivery. Antibody titers in the sera of the mothers remained elevated throughout this period. Electrocardiograms were recorded from groups of neonates from mothers with experimental SLE. The results indicated that a high percentage of the offspring had defects in their conduction system including first, second, and third degree heart block; significant bradycardia; and wide QRS complex. Normal patterns were observed in offspring of healthy mothers. Experiments done with mice that were exposed to SLE-related autoantibodies early in their development indicated that offspring to mothers with experimental SLE were neither protected nor more susceptible to disease induction by the 16/6 Id.

The influence of aging on the induction and manifestations of experimental systemic lupus erythematosus

The influence of age on autoimmunity was studied in a model in which experimental systemic lupus erythematosus (SLE) is induced in normal mice by the injection of a human monoclonal anti-DNA antibody expressing a common idiotype designated 16/6 Id. The resulting disease is expressed by the production of a variety of autoantibodies and clinical manifestations characteristic to human SLE. Female BALB/c mice, at ages of 2 and 12 months, were immunized with the 16/6 Id. Mice were tested periodically for the presence of autoantibodies. The production of all autoantibodies tested was significantly lower in the older mice as compared to the group of young mice. Clinical manifestations which included leukopenia, increased erythrocyte sedimentation rate and proteinuria were similar in both age groups. Kidney evaluations revealed differences among the two groups of mice. While in all kidney sections of young mice multiple immune complex deposits were detected, in the group of older mice half had similar pathology while the rest either were negative or had only segmental and partial glomerular immune complex depositions. Thus, aging is associated with a decrease in the capacity to respond to the pathogenic anti-DNA, 16/6 Id, by the production of antibodies and autoantibodies and in the expression of a milder disease.

Induction of experimental systemic lupus erythematosus (SLE) in mice with severe combined immunodeficiency (SCID)

A model in which experimental SLE is induced in normal mice by the injection of a human anti-DNA MoAb expressing a common idiotype 16/6 Id has been established in our laboratory. In the present study we have attempted the induction of experimental SLE in mice with SCID by the transfer of lymphocytes obtained from mice with experimental SLE. Disease could not be induced by direct immunization of SCID mice with the 16/6 Id nor by transfusion of normal splenocytes and immunization with the 16/6 Id thereafter. In contrast, disease was induced in SCID mice which were transplanted with splenic lymphocytes obtained from SLE afflicted BALB/c mice. The disease was expressed by the presence of high titres of antibodies and glomerular immune complex deposits were present in the kidney sections of these mice. Mice that received spleen cells from donors with experimental SLE together with the 16/6 Id developed higher titres of autoantibodies and had, in addition to the immune complex deposits, glomerular histological pathology. The model of experimental SLE induction in SCID mice should help in the elucidation of the role of different cell types in the pathogenesis of SLE.

Autoimmune mechanisms in thromboangiitis obliterans (Buerger's disease): the role of tobacco antigen and the major histocompatibility complex

This study is a continuation of our previous work that showed that patients with thromboangiitis obliterans (TAO; Buerger's disease) demonstrate a cell-mediated immune response to human artery type-specific collagens. To investigate the role of cigarette smoking in patients with TAO, cellular and humoral sensitivity was tested to a tobacco glycoprotein (TGP) antigen in 13 patients with Buerger's disease, 16 healthy smokers, and 12 nonsmoking healthy young male subjects. In this study, patients with Buerger's disease and healthy smokers had the same rate of cellular response to TGP, whereas nonsmokers did not respond. All three groups had a 30% to 40% measurable antibody response to TGP. If TGP has an immunologic role in the pathogenesis of TAO, an additional factor (or factors) may be operative. A specific genetic makeup may be one such factor, although at this stage other pathogenic mechanisms cannot be ruled out. Eleven patients with Buerger's disease and two control groups of 10 young healthy smoking male subjects and 12 young nonsmokers underwent histocompatibility leukocyte antigen (HLA) typing. Patients with Buerger's disease had a statistically significantly higher frequency of HLA-DR4 and a significantly lower frequency of the HLA-DRW6 antigen than had both control groups. Because similar findings have been reported in other autoimmune diseases, this observation may serve as further evidence that an autoimmune mechanism is involved in Buerger's disease.

A tale of two peptides, TyrTyrGluGlu and TyrGluTyrGlu, and their diverse immune behaviour

Studies on a synthetic multichain polypeptide antigen, (T,G)-A--L, prepared by polymerization techniques, led to a better understanding of the molecular basis of antigenicity, and of many other immunological phenomena, as well as to the discovery of determinant-specific genetic control of immune response. In view of the intensity of studies with this polymer, we were interested in elucidating its major B and T cell epitopes. We investigated two tetrapeptides, TyrTyrGluGlu and TyrGluTyrGlu. Both were attached to multichain branched poly(DLalanine). Even though the two resulting synthetic immunogens are essentially identical in their molecular weight, size, shape and composition, and differ chemically only in the sequence of the tetrapeptide epitopes, the immunological differences observed were profound. Antibodies in the two systems do not cross-react. The major B cell epitope of (T,G)-A--L is TyrTyrGluGlu, whereas the major T cell epitope is TyrGluTyrGlu. The two antigens are under different genetic controls, and differ in their uptake by macrophages. The TyrTyrGluGlu polymer is thymus-dependent, whereas the TyrGluTyrGlu polymer is thymus-independent. Investigation of the two tetrapeptides in their polymeric form, by photochemically induced dynamic nuclear magnetic polarization techniques, shows that they differ strongly in their intra-epitope aromatic interactions. Phenolic groups in TyrGluTyrGlu interact with each other, whereas they are far apart in TyrTyrGluGlu, as seen also in computer-derived models.

Direct binding of a synthetic multichain polypeptide to class II major histocompatibility complex molecules on antigen-presenting cells and stimulation of a specific T-cell line require processing of the polypeptide

T-cell activation involves the recognition of foreign antigens as a complex with self-major histocompatibility complex (MHC) proteins on the surface of antigen-presenting cells (APC). Protein antigens usually require uptake by the APC and processing that results in the generation of peptide fragments. The branched synthetic polypeptide (Tyr, Glu)-Ala--Lys was chosen as a model antigen to follow the processing requirements, leading to T-cell activation. It has been demonstrated, by using fixed APC and various inhibitors of proteases, that (Tyr, Glu)-Ala--Lys has to be processed to stimulate a (Tyr, Glu)-Ala--Lys-specific T-cell line of C3H.SW (H-2b) origin to proliferate. To determine whether processing of (Tyr,Glu)-Ala--Lys is required to allow its association with the MHC class II molecules, biotin was covalently attached to it. Binding of the biotinylated (Tyr,Glu)-Ala--Lys to MHC class II gene products on the surface of intact normal APC was directly detected by phycoerythrin-streptavidin. The specificity of the binding was confirmed by its inhibition with anti-I-Ab antibodies as well as with excess of nonlabeled (Tyr,Glu)-Ala--Lys. Furthermore, introducing several inhibitors of proteases to the binding assay, we could substantiate that the proteolysis of (Tyr,Glu)-Ala--Lys is required to allow association of the resulting peptidyl T-cell epitopes with the MHC class II molecules themselves. The presence of the biotin moiety in the resulting peptides suggests that the T-cell epitopes of (Tyr,Glu)-Ala--Lys contain the N-terminal portion of the side chains of the branched polypeptide. An apparent Kd of 8.05 x 10(-8) M was determined, and optimal binding was detected after 10 hr of incubation with the antigen. The latter phenomenon is not due to slow uptake, since uptake of (Tyr,Glu)-Ala--Lys occurs mainly during the first 30 min of incubation, but rather reflects the events of processing that precede MHC interaction.

Pathogenic anti-DNA idiotype (16/6 Id) in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is regarded as a classical autoimmune disease. Despite this belief, no one has been able to induce the disease in naive animals, neither with DNA nor with anti-DNA antibodies. We report on the induction of SLE in BALB/c mice following immunization with a pathogenic anti-DNA idiotype (16/6 Id) or its anti-Id. We also report on a specific treatment with T suppressor cells specific for the 16/6 Id. The induction of SLE in naive mice with a pathogenic anti-DNA Id suggests an additional mechanism for the diversity of manifestations in this disease.

Induction of systemic lupus erythematosus in naive mice with T-cell lines specific for human anti-DNA antibody SA-1 (16/6 Id+) and for mouse tuberculosis antibody TB/68 (16/6 Id+)

Previously we have shown the ability to induce experimental systemic lupus erythematosus (SLE) in naive mice with pathogenic antibodies carrying the 16/6 idiotype (Id) and with the T-cell line specific for the 16/6 Id. In the present study we established and characterized a series of T-cell clones that react against diverse autoantibodies carrying the 16/6 Id and show that they are capable of inducing a SLE-like disease in mice. The T-cell clones were generated from BALB/c mice immunized with the human mAb anti-DNA antibody (SA-1) and the mouse monoclonal anti-tuberculous Ab (TB/68), both carrying the 16/6 Id. The T-cell clones proliferated only in the presence of either human or mouse mAb carrying the 16/6 Id. All the T-cell clones were found to be of the helper type (L3T4) and were H-2 restricted in their function. The injection of the clones to BALB/c mice resulted in serological findings (e.g., anti-DNA, anti-Sm), clinical manifestations (e.g., proteinuria, low white blood cell counts, increased erythrocyte sedimentation rate), and renal insult typical of SLE disease. Our data support the role attributed to pathogenic idiotypes in SLE on the one hand and that played by cellular immunity on the other. The mechanism by which Id-specific T-helper cells may induce SLE is currently not clear. The immunogenicity of the T-cell receptor (anti-16/6) and the cells themselves acting as effector/helper cells, thus leading to damage, may play a role in initiating a chain of events that ends in the production of a panoply of autoantibodies, some of which may also have a regulatory function.

Idiotype specific T-cell lines inducing experimental systemic lupus erythematosus in mice

Immunization of mice with either antibodies bearing the 16/6 idiotype (16/6 Id) or anti-idiotypic antibodies against the 16/6 Id induces experimental systemic lupus erythematosus (SLE). We report here the establishment and characterization of 16/6 Id-specific T-cell lines from C3H.SW (H-2b) and BALB/c (H-2d) mice. Both lines proliferate specifically in response to the 16/6 Id in an H-2-restricted manner. The injection of 16/6 Id-specific T cells into syngeneic mice led to the development of experimental SLE. Furthermore, inoculation of the 16/6 Id-specific T-cell line derived from C3H.SW mice into the H-2 compatible C57BL/6 mice, which are non-responders to the 16/6 Id, induced experimental SLE. This report provides direct evidence for the role of idiotype-specific T cells in the induction of experimental SLE.

Progressive immune dysfunction in cats experimentally infected with feline immunodeficiency virus

Within 6 months of infection with the Petaluma isolate of feline immunodeficiency virus, specific-pathogen-free domestic cats exhibited a decrease in the percentage and number of circulating CD4+ lymphocytes and in the CD4+/CD8+ T-cell ratio, along with a marginally significant depression of pokeweed mitogen-induced lymphocyte proliferation in vitro. There was no loss of responsiveness to concanavalin A during this stage, and the cats were capable of mounting a satisfactory antibody response to a T-dependent, synthetic polypeptide immunogen. The pokeweed mitogen response deficit became clearly demonstrable by 11 to 12 months postinfection. A decline in the lymphocyte proliferative response to concanavalin A and a diminished ability to mount an in vivo antibody response to the T-dependent immunogen evolved by 25 to 44 months postinfection. Virus infection did not affect the ability of cats to mount an antibody response to a T-independent synthetic polypeptide immunogen. These data indicate that feline immunodeficiency virus produces a slowly progressive deterioration of T-cell function but does not affect the ability of B cells to recognize and respond to a T-independent antigenic stimulus.

Effects of aging on the induction of experimental systemic lupus erythematosus (SLE) in mice

The study was designed to determine whether manifestations of autoimmunity are altered with age, using an experimental model in which systemic lupus erythematosus (SLE) is induced in mice. Young (2-month-old), and aging (18-month-old) BALB/c female mice were immunized with a human monoclonal anti-DNA antibody that bears a common idiotype (16/6 Id). Control groups were either left untreated or were injected with human IgM (HIgM). Anti-16/6 Id levels were found to be significantly lower in the old mice than in the young. Similarly, anti-anti-16/6 Id (murine 16/6 Id+) values were lower in the old. Mice injected with the 16/6 Id also produced various autoantibodies, including anti-dsDNA, anti-RNP, anti-Sm and anti-histones antibodies. The levels of these antibodies were lower in the old mice than in the young, yet the differences were not statistically significant. Levels of autoantibodies examined in control animals were either similar in both age groups (anti-RNP and histones) or lower in the old (anti-dsDNA and Sm). Four months after a booster injection of 16/6 Id, the young mice developed clinical manifestations of SLE, including proteinuria and leukopenia, which were seen, in milder form, in the aged mice. Immune complex depositions examined by immunohistology on kidney sections suggested similar differences based on the age of the animals. Our results suggest that aging might actually be associated with a decline in the capacity to produce autoimmune responses.

Regulatory T cell activity specific to human type II and III collagens in rheumatoid arthritis

Fifty-one patients with rheumatoid arthritis (RA) were examined for their immune response potential to human collagen type II and III. It was found that T cells of 57% of patients with RA proliferated to collagen type III whereas only 27% of T cells of patients with osteoarthritis (OA) and healthy controls responded to this antigen by proliferation (p less than 0.04). A lower percentage (38%) of patients with RA had proliferative responses to collagen type II in comparison to 17% of responders in healthy controls. The capability to produce T cell helper factors specific to collagen type III was found to be significantly higher in patients treated with nonsteroidal antiinflammatory drugs (NSAID) (60%) in comparison to patients with OA (16%) and healthy controls (13%). Immunoregulatory drugs affected the specific T helper function in response to collagen type III but did not change the proliferative responses to collagen type II and III in patients with RA. HLA analyses revealed a significant difference in the frequency of HLA-DRw10 between our sample of patients with RA and healthy controls.

Specific proliferative responses following the induction of experimental SLE in mice

We have previously reported the induction of experimental systematic lupus erythematosus (SLE) in mice by immunization with a human monoclonal antibody that expresses a common anti-DNA idiotype (16/6 Id). Following immunization, antibodies directed against various nuclear autoantigens could be detected in the sera of the mice. In the present study, we investigated the proliferative responses of lymph node cells to one particular autoantigen (DNA) following the induction of experimental SLE. Cells reactive with ssDNA could be detected following immunization of BALB/c mice with the 16/6 Id. The appearance of these DNA-reactive cells succeeded the appearance of 16/6 Id-specific cells. The activation of this subset of autoreactive cells could be achieved only by the immunization of the mice with the 16/6 Id, but not by their immunization with DNA, thus suggesting that the induction of experimental SLE is associated with the alteration of the low responsive potential of the mice to DNA.