Antinuclear antibodies in rabbit antisera.

Antinuclear antibodies were detected by immunofluorescence in most sera from rabbits immunized with whole human serum emulsified in Freund's complete adjuvant. Four of 14 sera from rabbits immunized with Cohn fractions III, IV-1, or IV-4 also gave positive nuclear fluorescence with human leukocyte nuclei. Other human and animal nuclei gave negative results with these rabbit antisera. Three rabbit anti-whole human sera had complement-fixing antibody against DNA in sufficient titer for study in quantitative complement fixation tests. Antibody with greatest reactivity with human single strand DNA was detected in the 3 rabbit antisera. Reactivity with rabbit, calf thymus, and B. natto DNA was also detected. In each case reactivity was greater with single strand than with native DNA. Antibodies against human histone and purine-6-oly BSA were also detected. No correlation was found between the titers of rheumatoidlike factors and antinuclear antibodies present in the rabbit antisera. The induction of antinuclear antibodies in these rabbits was not associated with disease attributable to the antibodies. The induction of antinuclear antibody by immunization with whole human serum was interpreted as indicating the presence of antigenic nuclear material in whole human serum.

In vitro effects of Epstein-Barr virus on peripheral blood mononuclear cells from patients with rheumatoid arthritis and normal subjects.

Peripheral blood mononuclear cells from 10 patients with rheumatoid arthritis and 9 control subjects were cultured in vitro for 30 days with and without infection by Epstein-Barr virus. All cultures showed polyclonal stimulation of B cells as indicated by rising levels of IgM in the culture supernates, reaching maximal at 18-24 days, and with no quantitative or kinetic difference between the RA and control cells. IgM anti-IgG was also produced in both groups and maximally at 18-24 days, but in greater quantity by the RA lymphocytes. The anti-IgG made by the RA lymphocytes was more easily absorbed by solid phase IgG than was the anti-IgG made by the normal lymphocytes and thus was judged to be of higher affinity. RA lymphocytes uninfected with EBV had higher transformation scores than did the normal controls and developed spontaneously into permanent cell lines in six instances.

Autoantibodies in infectious mononucleosis have specificity for the glycine-alanine repeating region of the Epstein-Barr virus nuclear antigen.

Viruses have been postulated to be involved in the induction of autoantibodies by: autoimmunization with tissue proteins released by virally induced tissue damage; immunization with virally encoded antigens bearing molecular similarities to normal tissue proteins; or nonspecific (polyclonal) B cell stimulation by the infection. Infectious mononucleosis (IM) is an experiment of nature that provides the opportunity for examining these possibilities. We show here that IgM antibodies produced in this disease react with at least nine normal tissue proteins, in addition to the virally encoded Epstein-Barr nuclear antigen (EBNA-1). The antibodies are generated to configurations in the glycine-alanine repeat region of EBNA-1 and are crossreactive with the normal tissue proteins through similar configurations, as demonstrated by the effectiveness of a synthetic glycine-alanine peptide in inhibiting the reactions. The antibodies are absent in preillness sera and gradually disappear over a period of months after illness, being replaced by IgG anti-EBNA-1 antibodies that do not crossreact with the normal tissue proteins but that are still inhibited by the glycine-alanine peptide. These findings are most easily explained by either a molecular mimicry model of IgM autoantibody production or by the polyclonal activation of a germline gene for a crossreactive antibody. It also indicates a selection of highly specific, non-crossreactive anti-EBNA-1 antibodies during IgM to IgG isotype switching.

Characterization of human rheumatoid factors with seven antiidiotypes induced by synthetic hypervariable region peptides.

Recently, we have used synthetic peptides corresponding to the complementarity-determining regions (CDR) of Ig molecules to induce antiidiotypic antisera. Peptide PSH3, representing the third CDR of the IgM rheumatoid factor (RF) Sie heavy (H) chain, induced a private antiidiotype that reacted with only one out of five IgM-RF. Peptide PSL2, corresponding to the second CDR of Sie light (L) chain, induced an antibody against a crossreactive idiotype (CRI), expressed by 10 out of 12 human IgM-RF analyzed. Herein, we report that five additional antiidiotypic antibodies were generated by immunization with synthetic peptides identical to the third L chain CDR of IgM-RF Sie (PSL3), the second and third H chain CDR of IgM-RF Wol, and the second and third CDR of IgM-RF Pom. As analyzed by immunoblot assay, both anti-PSL3 and anti-PSL2 reacted with the majority of 16 IgM-RF. In contrast, all five antiidiotypes induced by the H chain peptides reacted only with the parent proteins, except anti-PSH3, which reacted weakly with one additional RF. These results suggest that one (or very few) VL gene(s), but a larger number of VH genes, are used to encode IgM-RF autoantibodies.

Delineation of a cross-reactive idiotype on human autoantibodies with antibody against a synthetic peptide.

Antibody against a cross-reactive idiotype (CRI) on human IgM-rheumatoid factor (RF) antibodies was induced by immunization of rabbits with a synthetic peptide ( PSL2 ) corresponding to the second complementarity-determining region (CDR), and adjacent amino acid residues of the kappa light chain of the IgM-RF Sie . The anti-peptide antibody bound efficiently to IgM-RF proteins known to share a cross-reactive idiotype, and to their isolated kappa chains. The anti-CRI was absorbed by, and eluted from, a peptide-Sepharose affinity column. The antibody activity was inhibited by the free peptide in solution. The anti-peptide antibody thus identifies a public idiotype on human IgM-RF, that is largely dependent on the primary sequence of the second CDR of the light chain. Such peptide-induced antiidiotypes of predefined specificity may facilitate studies of the molecular basis of idiotypic cross-reactions, the inheritance and somatic diversification of antibody molecules, and the regulation of the idiotype network.

Effect of neuropeptides on production of inflammatory cytokines by human monocytes.

Two groups of mediators, the neuropeptides substance P and K and the monocyte-derived cytokines, interact in the neural regulation of immunological and inflammatory responses. Substance P, substance K, and the carboxyl-terminal peptide SP(4-11) induce the release of interleukin-1, tumor necrosis factor-alpha, and interleukin-6 from human blood monocytes. The neuropeptide effects occur at low doses, are specific as shown by inhibition studies with a substance P antagonist, and require de novo protein synthesis. Since monocyte-derived cytokines regulate multiple cellular functions in inflammation and immunity and since neuropeptides can be released from peripheral nerve endings into surrounding tissues, these findings identify a potent mechanism for nervous system regulation of host defense responses.

Substance P activation of rheumatoid synoviocytes: neural pathway in pathogenesis of arthritis.

Several clinical features are consistent with nervous system involvement in the pathogenesis of rheumatoid arthritis. The neuropeptide substance P is one possible mediator of this interaction, since it can be released into joint tissues from primary sensory nerve fibers. The potential effects of the peptide on rheumatoid synoviocytes were examined. The results show that substance P stimulates prostaglandin E2 and collagenase release from synoviocytes. Furthermore, synoviocyte proliferation was increased in the presence of the neuropeptide. Similar effects were observed with a truncated form of substance P. Synoviocytes were sensitive to very small doses of the neuropeptide (10(-9) M), and its effects were inhibited by a specific antagonist. Thus, the specific stimulation of synoviocytes by the neuropeptide substance P represents a pathway by which the nervous system might be directly involved in the pathogenesis of rheumatoid arthritis.

The detection of cell-bound antibody on complement-coated human red cells.

This study sought to elucidate the mechanism by which human red cells, in a variety of clinical settings, become coated in vivo with autologous complement components in the absence of anti-red cell autoantibodies demonstrable by standard methods. By means of a newly developed complement-fixing antibody consumption test, previously undetectable red cell-bound gammaG globulin could be detected and quantified. By this technique, the complement-coated red cells of 13 of 16 patients were shown to carry abnormally high numbers of gammaG molecules per cell, which were nevertheless below the level for detection by the direct antiglobulin test. Eluates were made from the red cells of seven of these patients and each eluate, when sufficiently concentrated, was capable of sensitizing normal human red cells (with gammaG antibodies) to give a positive indirect antiglobulin test with anti-gammaG serum. In the presence of fresh normal serum, six of the eluates so tested were capable of fixing complement to normal human red cells. The antibodies in the red cell eluates did not exhibit Rh specificity and did not react with nonprimate red cells. When studied by sucrose gradient ultracentrifugation, the gammaG antibodies to human red cells in these eluates sedimented in the 7S region. It is concluded that in many patients in whom direct antiglobulin tests reveal only cell-bound complement, the complement fixation is mediated in vivo by small quantities of "warm-reacting" erythrocyte autoantibodies of the gammaG class.

Light and heavy chain components of gamma globulins in urines of normal persons and patients with agammaglobulinemia.

A heavy chain component of gammaG-globulins in normal urines has the characteristics of the proteolytic digestion product, Fc-fragment. This fragment is estimated to compose up to 15% of the gamma globulins present in urines. In contrast to urinary light chains, the urinary Fc-like fragment probably represents a catabolic component in normal gammaG-globulin metabolism. The light chains of the urine constitute more than half the total gamma globulin present. The calculated kappa/lambda ratio of light chains averaged 1.9 in ten urines, but the ratio in individual urines varied widely to either side of this figure. In two adult patients with agammaglobulinemia whose sera contained less than one-hundredth the normal gamma globulin levels, the urinary Fc-like fragment was absent, whereas the light chain levels were only one-tenth the average normal level. Treatment with exogenous gamma globulins resulted in normal or near normal Fc-like fragment excretion, whereas light chain excretion was only modestly affected.

Increased production and expression of tissue thromboplastin-like procoagulant activity in vitro by allogeneically stimulated human leukocytes.

Intravascular coagulation, thrombosis, and fibrin deposition often produce tissue damage in allogeneic inflammatory reactions such as allograft rejection. The mechanisms which initiate blood clotting in these reactions are poorly understood. We find that allogeneic stimulation of human leukocytes in vitro increases production and expression of tissue thromboplastin-like activity. In our experiments mixed leukocyte cultures (MLC) of cells from allogeneic (unrelated) donors produced and expressed more procoagulant activity than control cultures of cells from each donor alone. After 7 days, allogeneic MLC had 5- to 50-fold more total procoagulant activity than controls, as shown by assaying lysed whole cultures. Additionally, allogeneic MLC had 8- to 240-fold more procoagulant activity expressed on leukocyte surfaces and in culture supernates than controls after 7 days, as shown by assaying intact whole cultures and cell-free supernates. These increases were largely accounted for by gains in the amounts of procoagulant activity produced and expressed per cell in MLC as compared to controls. Controls and MLC produced and expressed considerable amounts of procoagulant activity during the 1st day of culture, and there were no differential effects of allogeneic stimulation on day 1. However, after day 1, the total amount of procoagulant activity produced and the amount expressed declined steadily in controls, nearly reaching preculture levels by day 7. In contrast, the total amount of procoagulant activity in allogeneic MLC remained high, and the amount of activity expressed on cell surfaces and in supernates increased severalfold by day 7. MLC of syngeneic (identical twin) cells produced and expressed the same amount of activity as controls over a 7-day period, whereas MLC of cells from each twin and an allogeneic donor produced and expressed more activity than controls (at least 9- and 35-fold more, respectively). Thus, increases of procoagulant activity production and expression were found only in MLC of genetically dissimilar cells. Therefore, these increases must have resulted from allogeneic stimulation.

Leukocyte procoagulant activity: enhancement of production in vitro by IgG and antigen-antibody complexes.

In a variety of immunologic diseases, fibrin-fibrinogen and immune complexes deposit in areas of tissue damage. However, the mechanisms which initiate fibrin-fibrinogen deposition have not been clarified. We find that the procoagulant activity of human leukocytes is markedly increased after incubation with immunoglobulin and immune complexes. This procoagulant activity is evident after 4-24 h incubation in the presence of as little as 0.1 mg/ml of autologous, isologous, or heterologous IgG. At least three of the four subclasses of IgG myeloma proteins are effective. Experiments with purified rabbit and rat antibodies demonstrate that enhancement of procoagulant activity is significantly greater with soluble antigen-antibody complexes than with immunoglobulin alone. In contrast, insoluble complexes are less affective than immunoglobulin alone. Artifacts due to endotoxin contamination of the IgG preparations were excluded on the basis of the differential sensitivities of immunoglobulin and endotoxin to heat and polymyxin B. Evidence is also presented which shows that enhancement of procoagulant activity involves the production, rather than a simple release, of leukocyte procoagulant activity in vitro.

Studies with human leukocyte lysosomes. Evidence for antilysosome antibodies in lupus erythematosus and for the presence of lysosomal antigen in inflammatory diseases.

Human lysosomes were isolated from normal peripheral blood leukoyctes and characterized by electron microscopy, enzyme analysis, and assays for DNA and RNA. Stored sera from 37 unselected patients with systemic lupus erythematosus (SLE), including active and inactive, treated and untreated cases, were tested in complement fixation (CF) reactions with these lysosome preparations. 23 SLE sera exhibited positive CR reactions, as did sera from two patients with "lupoid" hepatitis. The seven SLE sera with strongest CF reactivity also demonstrated gel precipitin reactions with lysosomes. Neither CF nor precipitin reactions with lysosomes were observed with normal sera or with sera of patients with drug-induced lupus syndrome, rheumatoid arthritis (RA), polymyositis, or autoimmune hemolytic anemia. By several criteria the antilysosome CF and precipitin reactions of SLE sera cound not be attributed to antibody to DNA, RNA, or other intracellular organelles. The lysosomal component reactive with SLE sera in CF assays was sedimentable at high speed and is presumably membrane associated. The CF activity of two representative SLE sera was associated with IgG globulins by Sephadex filtration. A search for lysosomal antigen in SLE and related disorders was also made. By employing rabbit antiserum to human lysosomes in immunodiffusion, a soluble lysosomal component, apparently distinct from the sedimentable (membrane-associated) antigen described above, was identified in serum, synovial fluid, or pleural fluid from patients with SLE, RA, ankylosing spondylitis, and leukemoid reaction. An antigenically identical soluble component reactive with the rabbit antiserum could be released in vitro from intact lysosomes by repeated freeze-thaw cycles..

Complement fixation by rheumatoid factor.

The capacity for fixation and activation of hemolytic complement by polyclonal IgM rheumatoid factors (RF) isolated from sera of patients with rheumatoid arthritis and monoclonal IgM-RF isolated from the cryoprecipitates of patients with IgM-IgG mixed cryoglobulinemia was examined. RF mixed with aggregated, reduced, and alkylated human IgG (Agg-R/A-IgG) in the fluid phase failed to significantly reduce the level of total hemolytic complement, CH50, or of individual complement components, C1, C2, C3, and C5. However, sheep erythrocytes (SRC) coated with Agg-R/A-IgG or with reduced and alkylated rabbit IgG anti-SRC antibody were hemolyzed by complement in the presence of polyclonal IgM-RF. Human and guinea pig complement worked equally well. The degree of hemolysis was in direct proportion to the hemagglutination titer of the RF against the same coated cells. Monoclonal IgM-RF, normal human IgM, and purified Waldenström macroglobulins without antiglobulin activity were all inert. Hemolysis of coated SRC by RF and complement was inhibited by prior treatment of the complement source with chelating agents, hydrazine, cobra venom factor, specific antisera to C1q, CR, C5, C6, or C8, or by heating at 56 degrees C for 30 min. Purified radiolabeled C4, C3, and C8 included in the complement source were bound to hemolysed SRC in direct proportion to the degree of hemolysis. These data indicate that polyclonal IgM-RF fix and activate complement via the classic pathway. The system described for assessing complement fixation by isolated RF is readily adaptable to use with whole human serum.

Inheritance of immunoglobulin M rheumatoid-factor idiotypes.

The idiotypic determinants on IgM rheumatoid factor (RF) from a single family have been analyzed. Rabbit Fab'2 antiidiotypic antibody was prepared against purified IgM-RF from a patient with rheumatoid arthritis. As measured by radioimmunoassay, the antiidiotype reacted with at least 90% of the patient's RF, but not with non-RF immunoglobulins from the same serum, nor with 10 of 11 polyclonal and monoclonal RF from unrelated individuals. Cross-reacting idiotypes were detected on RF in four of the patients' first degree relatives, spanning three generations, without apparent relation of HLA type or clinical rheumatoid arthritis. These results suggest that IgM-RF associated idiotypes were inherited in this family.

Antibody to the rheumatoid arthritis nuclear antigen. Its relationship to in vivo Epstein-Barr virus infection.

Most patients with seropositive rheumatoid arthritis, and a variable but lesser percentage of normal subjects, have precipitating antibodies to a nuclear antigen, rheumatoid arthritis nuclear antigen, present in Epstein-Barr virus-infected human B lymphoblastoid cells. We have used a sensitive indirect immunofluorescence assay for antibody to rheumatoid arthritis nuclear antigen in a study of patients with infectious mononucleosis and healthy control subjects. Of 110 sera from normal, college-age cadets, 58 were from individuals without prior Epstein-Barr virus infection, as indicated by the lack of antibody to viral capsid antigen. All of these also lacked activity to rheumatoid arthritis nuclear antigen. 52 sera were positive for antibody to viral capsid antigen, and antibody to rheumatoid arthritis nuclear antigen was present in 26 (50%) of these. In 67 sequential sera from 11 college-age students with infectious mononucleosis who became positive for antibody to rheumatoid arthritis nuclear antigen, only 2 were positive during the 1 mo. Thereafter the incidence and titers increased progressively through the 1st yr after infection. This time-course resembled that for the development of antibody to Epstein-Barr nuclear antigen, another transformation antigen in Epstein-Barr virus-infected B lymphocytes. The development of positivity for both was much later than that of antibody to the structural viral capsid antigen, which in the current study was always positive by 1 wk. Thus, antibody to rheumatoid arthritis nuclear antigen is present in a large proportion of normal individuals and can now be clearly ascribed, from both in vivo and in vitro studies, to prior infection with Epstein-Barr virus.

Synovium as a source of interleukin 6 in vitro. Contribution to local and systemic manifestations of arthritis.

Synovial inflammation is often associated with systemic changes, such as increased levels of acute phase proteins and hypergammaglobulinemia, which cannot be explained by the cytokines described in synovial fluids and synoviocyte secretions. Interleukin 6 (IL-6) has recently been characterized as a mediator of multiple inflammatory responses. This cytokine promotes T and B lymphocyte growth and differentiation, and acute phase protein synthesis. We therefore examined IL-6 production by human synoviocytes and its presence in synovial fluids. In vitro, synoviocytes spontaneously released IL-6, which was increased by IL-1 and tumor necrosis factor-alpha. Synoviocyte-derived IL-6 activity was able to induce hybridoma-plasmacytoma proliferation, and immunoglobulin and acute-phase protein synthesis. The synovial fluids from patients with diverse arthropathies contained IL-6 activity, but higher levels were present in inflammatory arthropathies than in osteoarthritis. These results demonstrate that synoviocytes are a potent source of IL-6, which can contribute to important manifestations of inflammatory arthropathies.

Basis for defective responses of rheumatoid arthritis synovial fluid lymphocytes to anti-CD3 (T3) antibodies.

Synovial fluid mononuclear cells (SFMC) from patients with active rheumatoid arthritis characteristically respond poorly to mitogens. In this study, mitogenic antibodies reactive with the CD3(T3) antigen on human T lymphocytes were used to analyze the basis for the deficiency. OKT3-induced proliferation and release of interleukin 1 (IL-1) and interleukin 2 (IL-2) from SFMC were depressed in all patients. Purified IL-1 or recombinant IL-2 restored proliferative responses in SFMC and increased IL-2 receptor density. Exogenous IL-1 also enhanced IL-2 release. Fractionation of SFMC supernatants on phosphocellulose columns revealed the presence of IL-1 and a potent IL-1 inhibitor. The monocyte-derived IL-1 inhibitor blocked IL-1-dependent responses of normal peripheral blood lymphocytes to OKT3, but had no effect on IL-2-dependent events. These results suggest that IL-1 inhibitor(s) in SFMC impair(s) OKT3-induced mitogenesis by interfering with the effects of IL-1 on T lymphocytes. The net result is deficient IL-2 secretion, IL-2 receptor expression, and impaired cellular proliferation. This novel inhibitory circuit provides a rational explanation for the diminished function of synovial fluid T lymphocytes in rheumatoid arthritis patients.

Epstein-Barr virus-induced autoimmune responses. II. Immunoglobulin G autoantibodies to mimicking and nonmimicking epitopes. Presence in autoimmune disease.

During infectious mononucleosis, IgM autoantibodies are generated to a protein, p542, which contains a glycine-rich 28-mer epitope cross-reactive with the Epstein-Barr nuclear antigen-1 through Epstein-Barr nuclear antigen-1's glycine/alanine repeat. In normal individuals it is uncommon to find IgG anti-p542, but among patients with progressive systemic sclerosis, systemic lupus erythematosus, and ulcerative colitis high IgG anti-p542 (> 3 SD above the mean of normal 20-50 yr controls) occurred frequently. Lesser elevations occurred in Sjögren's syndrome, rheumatoid arthritis, ankylosing spondylitis, and Crohn's disease, but none with chronic hepatitis B infection. The reactive epitopes on p542 were mapped with deletion mutants, which indicated that the glycine-rich 28-mer was the major antigenic determinant, with lesser antibody responses to other epitopes. We conclude that normally there is an inability to generate IgG autoantibodies to the cross-reactive (mimicking) epitope of the p542 host protein, but that this inability is overcome in a proportion of patients with autoimmune disease. We conclude also that non-cross-reactive autoepitopes exist on p542 protein, to which IgG autoantibodies can commonly be formed in autoimmune disorders. The mechanisms responsible for the latter must involve different mechanisms than those responsible for autoantibodies to the mimicking epitope.

Rheumatoid factor-producing cells detected by direct hemolytic plaque assay.

Lymphocytes secreting anti-IgC antibodies, rheumatoid factors (RF), can be detected in the peripheral bloods, synovial fluids, and bone marrows of patients with seropositive rheumatoid arthritis by using a direct plaque-forming cell (PFC) assay with sheep erythrocytes sensitized with reduced and alkylated rabbit IgG hemolysin. The autospecific nature of the RF produced by RF-PFC was indicated by inhibition studies in which the order of patency was human IgG greater than rabbit IgG greater than bovine IgG. In metabolic studies puromycin, cycloheximide, and venblastine suppressed RF-PFC. Cyclic AMP and cyclic GMP were without effect. A need was recognized for using full tissue culture media during the cell separation and plaquing procedures to optimize detection of the RF-PFC. RF-PFC may appear in the blood of patients intermittently despite their continuing presence in the bone marrow. They have been found in the peripheral blood, especially during acutely exacerbating polyarticular synovitis, generalized vasculities, or generally active, aggressive disease. RF-PFC were found in synovial effusions of new or recrduescent acute synovitis. RF-PFC were observed to disappear from the peripheral circulation and the bone marrow during therapy with cytotoxic drugs. The data are consistent with the hypothesis that the appearance of RF-PFC in the peripheral blood represents an anamnestic response to transiently appearing antigen. The nature of the antigen is not specified. The bone marrow may be a site of origin of RF-PFC.

Metabolism of autologous and homologous IgG in rheumatoid arthritis.

The metabolism of radioiodinated IgG was studied in 20 patients with rheumatoid arthritis and 11 normal controls using autologous IgG and homologous IgG pooled from normal donors. Fractional catabolic rates in the controls were 4.44% of the autologous- and 4.29% of the homologous-labeled protein per day. The corresponding rates in the rheumatoid patients were 9.67% of the autologous- and 8.64% of the homologous-labeled protein per day. Extravascular catabolism occurred only in the rheumatoid group and accounted essentially for the entire increased catabolism of IgG observed in these patients. 10 patients were especially hypercatabolic, with fractional catabolic rates for autologous IgG greater than 10%. Moreover, they catabolized their autologous IgG significantly faster than the homologous IgG (12.6 vs. 9.9%). The increment of catabolism of autologous over homologous IgG also occurred in the extravascular compartment. These highly hypercatabolic patients had a significantly increased number of manifestations of extra-articular disease. The hypercatabolism of IgG could not be correlated with age, weight, sex, duration of disease, joint erosions, corticosteroid therapy, erythrocyte sedimentation rate, rheumatoid factor titer, serum IgG concentration, or circulating immune complexes as measured by the Raji cell radioimmunoassay. Conceivable sites of extravascular catabolism and possible causes of faster catabolism of autologous (rheumatoid) than of homologous (normal) IgG are discussed.