Reactivity of anti-proliferating cell nuclear antigen (PCNA) murine monoclonal antibodies and human autoantibodies to the PCNA multiprotein complexes involved in cell proliferation

Proliferating cell nuclear Ag (PCNA) occurs as a component of multiprotein complexes during cell proliferation. We found the complexes to react with murine anti-PCNA mAbs, but not with anti-PCNA Abs in lupus sera. The complexes were purified from rabbit thymus extract by affinity chromatography using anti-PCNA mAbs (TOB7, TO17, and TO30) and analyzed by ELISA, immunoprecipitation, immunoblotting, and HPLC gel filtration. That PCNA was complexed with other proteins was demonstrated by its copurification with a group of proteins excluded by an HPLC G3000 SW column. Although immunoblot analysis showed the mAbs to react exclusively with the 34-kDa PCNA polypeptide, they nonetheless immunoprecipitated the same group of proteins, confirming the interaction of the isolated PCNA with other proteins. Anti-PCNA sera, including AK, which reacts with biologically functional sites on PCNA, did not react with complexed PCNA, but did react with it once it was dissociated from the complexes. PCNA complexes in turn reacted with murine anti-DNA mAbs, as well as with Abs against p21, replication protein A, DNA helicase II, cyclin-dependent kinases 4 and 5, and topoisomerase I. These findings suggest that the PCNA complexes purified using anti-PCNA mAbs comprise the "protein machinery" for DNA replication and cell cycle regulation. They also suggest that anti-PCNA mAbs are useful tools with which to characterize the protein-protein interactions within PCNA complexes, as well as the autoimmune responses to proteins interacting with PCNA, which may shed light on the mechanisms of autoantibody production in lupus patients.     

Identification of an acidic ribosomal protein reactive with anti-Sm autoantibody

Autoantibody to Sm Ag is a highly specific marker for the diagnosis of SLE. The Sm Ag exists in the cell nucleus as part of a ribonucleoprotein complex containing five small nuclear RNA. The major immunoreactive Sm species have been reported to be three polypeptides of m.w. 28,000/29,000 (B/B') and 16,000 (D). We report here that a m.w. 21,000 peptide is another major target of anti-Sm antibody. This peptide was originally identified by Western blotting as an acidic ribosomal protein (RP21) reactive with IgG from some SLE patients. Anti-RP21 is distinct from anti-ribosomal P protein antibody (anti-P) which has been previously identified as a lupus-specific autoantibody. Cell fractionation experiments showed that RP21 existed only in the ribosomal fraction and was never detected in other cellular compartments including nuclei. However, when nuclear extracts were used as Ag sources in immunoblotting, affinity-purified anti-RP21 was found to react with m.w. 28,000 and 16,000 peptides, suggesting that anti-RP21 reactivity might be due to the cross-reaction of anti-Sm. This was further confirmed by the evidence that two kinds of murine anti-Sm mAb independently derived from MRL/lpr mouse recognized RP21. These results indicate that anti-Sm antibodies in SLE are reactive with both nuclear and ribosomal ribonucleoproteins. Previous reports have described certain similarities, i.e., antibody subclass restriction and incidence, of anti-Sm and anti-P in both humans and autoimmune mice. Our present study demonstrated a close physical association of target molecules reactive with anti-Sm and anti-P, and might, therefore, provide some clue to the origin of these two types of lupus-specific autoantibodies.     

Molecular heterogeneity of the bullous pemphigoid antigens as detected by immunoblotting

Sera from 28 patients with bullous pemphigoid (BP), four patients with cicatricial pemphigoid (CP), and 24 controls (normal volunteers and patients with pemphigus, systemic lupus erythematosus, or other skin diseases) were tested against extracts of human epidermis by immunoblotting techniques. The extraction buffer included 1% SDS, 5% beta-mercaptoethanol, and six protease inhibitors with various specificities. BP sera from individual patients showed different patterns of reactivity with the same epidermal extract, and each pattern consisted of one or more bands. A total of five bands of 240 kD, 200 kD, 180 kD, 97 kD, and 77 kD reacted with BP sera; the 240-kD band reacted with one CP sera, and none of these bands was detected by the control sera. The 240-kD and 180-kD bands reacted very strongly with some sera and were most frequently observed (43% and 29%, respectively). The 200-kD, 97-kD, and 77-kD bands were less frequently observed (25%, 7%, and 7%, respectively), but when present, their reactions were usually strong. Eleven percent of the BP sera did not react with any bands. Contrary to previous reports, this study shows that BP autoantibodies react with several protein bands, as detected by immunoblotting. We have recently shown by immunoelectron microscopy that BP autoantibodies bind to the basal cell hemidesmosomes. It remains to be determined which of these protein bands represent specific hemidesmosomal proteins and which antibody-antigen interactions are relevant to the pathogenesis of this disease.     

Decreased levels of serum platelet-activating factor acetylhydrolase in patients with rheumatic diseases

PAF is a potent inflammatory compound known to stimulate the release of various cytokines involved in rheumatic diseases. Elevated blood PAF levels are reported in these patients. We report that serum PAF acetylhydrolase activity (AHA) levels are decreased in patients with rheumatoid arthritis or osteoarthritis as compared to healthy controls. Serum and synovial fluid AHA levels were correlated in these patients. The present study suggests the potential role of AHA in controling systemic and/or local PAF levels in patients with rheumatic diseases.     

Molecular cloning of a major CENP-B epitope and its use for the detection of anticentromere autoantibodies

An enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of anticentromere autoantibodies in sera of patients with suspected or manifest rheumatic diseases. The antigen source used in this assay consists of the recombinant protein of glutathione S-transferase (GST) fused to the last 60 C-terminal amino acid residues of the major centromere protein CENP-B. Although this CENP-B segment is only a small part of the complete polypeptide, we show that it constitutes an important autoimmune antigenic domain which is recognized by all patient sera in which ACA can be detected using the immunoblotting technique with a HeLa S3 nuclear protein extract as antigen source.     

Evaluation of microcirculatory disturbances in patients with rheumatic diseases by the method of diffuse reflectance spectroscopy

Immunoinflammatory reactions affecting the state of the microvasculature play the key role in the genesis of rheumatic diseases. Therefore, it is important to develop new methods for the early detection of microcirculatory disorders. The purpose of this study was to assess the possibilities of diffuse reflectance spectroscopy used to identify microcirculatory disturbances in patients with rheumatic diseases by measuring skin blood supply and oxygenation rate and their relationship with the varying degrees of inflammatory activity. A total of 36 patients with rheumatic diseases and 31 healthy volunteers took part in the study. We analyzed the skin diffuse reflectance spectra recorded on the palmar side of the distal phalange of the right middle finger using a FLAME spectrometer. The erythema index and saturation rate were calculated to quantify the content of hemoglobin and oxygen saturation of tissues in both groups. The differences in the parameters under study between the groups were found to be statistically significant. The average value of erythema index was twofold higher in patients with rheumatic diseases with the second degree of inflammatory activity and about 2.5-fold higher in patients with the third degree of inflammatory activity, compared to the control group. This fact indicates impaired blood circulation with increased blood flow caused by inflammatory processes. Thus, diffuse reflectance spectroscopy can be used as an additional non-invasive diagnostic test for assessing the severity of microcirculatory disturbances and the activity of inflammation in rheumatic diseases.     

Autoantibodies against a specific nuclear RNP protein in sera of patients with autoimmune rheumatic diseases associated with myositis

Polymyositis is an autoimmune, inflammatory disease affecting human skeletal muscle. In the presence of concomitant vasculitis in the skin, the term dermatomyositis is used. In contrast, systemic lupus erythematosus (SLE) is a multisystem disease in which involvement of the skin, kidneys, joints, brain, and other organs may be found. The clinical manifestations vary according to the organ/system involved. It is clinical and therapeutic importance to define which organ/system is involved during the course of the disease. We approached this problem by studying the specificity of autoantibodies that are generated in patients with SLE and polymyositis/dermatomyositis. Among such antibodies are those directed against nuclear components including a variety of ribonucleoprotein (RNP) complexes. We have utilized mammalian nuclear preparations enriched with RNP particles as the antigenic source for immunoblotting studies to identify specific antigenic polypeptides. In the study reported here, sera from five groups of patients were examined: 10 patients with dermatomyositis/polymyositis; six patients with SLE and myositis; 12 lupus patients with cerebral and/or renal disease; eight patients with SLE but no myositis, renal, or cerebral disease; and 5) 11 patients with muscle weakness or muscle disease not due to myositis. In the first two groups of patients with myositis, antibodies against a nuclear RNP protein of 56 KD was identified in 12 of 16 sera. In contrast, such antibodies were found in the serum of only two of 20 patients with SLE but without muscle involvement (groups 3 and 4), and were not found at all in patients with other muscle diseases. This study has identified a new marker, antibodies against a nuclear RNP protein of 56 KD for detecting muscle involvement among the autoimmune rheumatic diseases.     

Depletion of CD8+ cells exacerbates organ-specific autoimmune diseases induced by CD4+ T cells in semiallogeneic hosts with MHC class II disparity

Autoimmune diseases are known to be induced in some donor-recipient combinations of mice undergoing the graft-vs-host reaction (GVHR). In this paper, we report on the development of primary biliary cirrhosis (PBC)-like hepatic lesions and also on pancreatic insulitis in (B6 x bm12)F1 mice injected with B6 CD4+ T cells. At the sites of these lesions, cellular infiltration around ductal structure was observed. Immunohistochemical studies revealed that both CD4+ and CD8+ T cells were present in the lesions of the liver and pancreas. To clarify the role of the CD8+ T cells, which were probably of host origin, we used a mAb against the Lyt-2 molecule. Both the PBC-like hepatic lesions and pancreatic insulitis were exacerbated by eliminating CD8+ T cells from mice with MHC class II GVHR. Also, autoantibodies against the pyruvate dehydrogenase-E2 component, which has been recently found to contain an immunodominant site (autoepitope) for B cell reactivity in patients with PBC, were detected in the sera of these mice by ELISA and their presence was confirmed by immunoblotting procedures. Our findings suggest that similar mechanisms as in GVHR caused by MHC class II disparity are active in the development of PBC. It should also be noted that, in addition to the hepatic lesions, insulitis closely resembling that seen in the nonobese diabetic mouse was induced in our experimental system. The results suggest that our model provides a unique opportunity to study organ-specific autoimmune diseases. Because the effector in our experimental system was defined to be CD4+ T cells responding to Iabm12 Ag, our findings support the hypothesis that an excessive immune response directed against Ia Ag can produce autoimmune disease.     

Emerging role of anti-tumor necrosis factor therapy in rheumatic diseases

Tumor necrosis factor alpha (TNF-alpha) is an inflammatory cytokine that has been implicated in a variety of rheumatic and inflammatory diseases. New understanding of the importance of TNF-alpha in the pathophysiology of rheumatoid arthritis and Crohn's disease led to the development of a new class of targeted anti-TNF therapies. Anti-TNF-alpha agents including etanercept (a fusion protein of the p75 TNF receptor and IgG1) and infliximab (a chimeric monoclonal antibody specific for TNF-alpha) have been approved for the treatment of rheumatoid arthritis. In addition, infliximab has been approved in the treatment of patients with active or fistulating Crohn's disease. A new appreciation of the importance of TNF-alpha in other rheumatic and inflammatory diseases has led to a broadening of the application of anti-TNF agents. Both etanercept and infliximab have been used in open-label and randomized studies in patients with psoriatic arthritis. Although larger randomized trials are needed to confirm early results, both these anti-TNF-alpha agents, etanercept and infliximab, have demonstrated activity in improving the signs and symptoms of psoriatic arthritis and psoriasis. Infliximab has also been shown to be effective in patients with other rheumatic diseases, including ankylosing spondylitis, and may be effective in adult-onset Still's disease, polymyositis, and Beh?et's disease. Further investigations will fully elucidate the role of infliximab in these and other rheumatic diseases.     

Structural and functional analysis of monomorphic determinants recognized by monoclonal antibodies reacting with the HLA class I alpha 3 domain.

To identify mAb reacting with the HLA class I alpha 3 domain, 14 mAb recognizing monomorphic determinants expressed on HLA-A, B, and C Ag or restricted to HLA-B Ag were screened in indirect immunofluorescence with mouse L cells expressing HLA-B7/H-2Kb chimeric Ag. mAb CR1S63, CR10-215, CR11-115, and W6/32 were found to react with the HLA class I alpha 3 domain in addition to the alpha 2 domain. mAb Q1/28 and TP25.99 were found to react only with the HLA class I alpha 3 domain. The determinants recognized by the six mAb were mapped on the HLA class I alpha 3 domain by indirect immunofluorescence staining of L cells expressing H-2Kb Ag containing different segments of the HLA-B7 alpha 3 domain chimerized with the H-2Kb alpha 3 domain. mAb TP25.99 reacts with chimeric Ag containing the HLA-B7 184 to 199 stretch, mAb CR10-215 and CR11-115 react with chimeric Ag containing the HLA-B7 184 to 246 stretch, mAb CR1S63 and Q1/28 react with chimeric Ag containing the HLA-B7 184 to 256 stretch, and mAb W6/32 reacts with chimeric Ag containing the whole HLA-B7 alpha 3 domain. Functional analysis using human CD8 alpha-bearing mouse H-2Kb-specific T cell hybridoma cells (HTB-Leu2) showed that only mAb TP25.99 inhibited IL-2 production by HTB-Leu2 cells stimulated with L cells expressing KbKbB7 Ag. This inhibition may occur because of the spatial proximity of the determinant defined by mAb TP25.99 to the CD8 alpha binding loop and/or because of change(s) in the conformation of the CD8 alpha binding loop induced by the binding of mAb TP25.99 to the HLA class I molecule. Furthermore, mAb TP25.99 inhibited the cytotoxicity of CD8-dependent and CD8-independent CTL clones. These results indicate that mAb TP25.99 has unique specificity and functional characteristics. Therefore it represents a valuable probe to characterize the role of the HLA class I alpha 3 domain in immunologic phenomena.     

Requirements for the adoptive transfer of antibody responses to a priming antigen in man

Antibody responses to recall vaccines can be adoptively transferred after marrow transplantation in man. Transfer of responses to priming Ag has not been successful, although this would broaden the range of organisms to which recipients could be protected. To investigate the importance of T cells and Ag in such transfer we primed marrow donors with keyhole limpet hemocyanin (KLH) 1 or 3 wk before marrow harvesting. B cells secreting IgM and IgG anti-KLH antibody were present in donor marrow at both 1 and 3 wk after immunization. After T cell depletion, donor marrow was infused into chemo-irradiated recipients, half of whom were immunized pretransplant with KLH. We found no evidence for the transfer of the IgM component of the response. Clonal expansion of the transferred IgG antibody-secreting cells with a corresponding rise in recipient serum IgG antibody levels was seen only when donors were primed 3 wk before marrow harvest and when the recipients were also immunized. IEF and immunoblotting demonstrated that successful transfer coincided with maturation of the IgG primary response from a polyclonal to an oligoclonal pattern and confirmed that donor oligoclonal bands appeared in the recipient serum. We conclude that the immunization protocols required for the transfer of antibody responses to priming Ag reflect the initial dependence of unprimed B cells on T cell help and on prolonged Ag stimulation. Ag-stimulated primary B cells in T cell-depleted marrow respond only to the noncognate growth and differentiation signals available in the chemo-irradiated recipient after an initial period of clonal selection and expansion in the donor which is both T cell and Ag dependent. Even after this initial selection, continued expansion of antibody-secreting clones in recipients retains an absolute dependence on Ag stimulation. Immunization techniques to protect transplant recipients against organisms such as Pseudomonas and CMV may need to be modified accordingly.     

Human monoclonal antibodies reactive with antigens of the group A Streptococcus and human heart

Human mAb were produced from tonsillar or PBL of normal individuals or patients infected with group A streptococci. Lymphocytes were purified on Ficoll-Hypaque gradients and stimulated in vitro with purified group A streptococcal membranes or M protein extracts. The mAb were selected for study based on their reaction with group A streptococci, pep M5 protein, and/or M6 Escherichia coli protein. Further analysis by Western immunoblot or competitive inhibition ELISA revealed that there were two types of antibodies: one type that reacted with myosin and DNA and the other type that reacted with myosin, keratin, and/or actin. The specificities of these human mAb are similar to specificities observed in our previous studies of murine mAb reactive with group A streptococci and heart Ag. For comparison, anti-myosin antibodies were affinity purified from the sera of infected or acute rheumatic fever patients and were shown to react with myosin and DNA as well as with group A streptococci and M protein. To affinity purify these antibodies from normal sera, five times the amount of sera was required to obtain detectable quantities. These data suggest that the human mAb reactive with group A streptococci and myosin reflect the antibodies seen in sera from infected patients or acute rheumatics and that the B lymphocyte clones capable of producing these cross-reactive antibodies are also present in normal individuals.     

Total radical-trapping antioxidative capacity of plasma and whole blood chemiluminescence in patients with inflammatory and autoimmune rheumatic diseases

The total radical-trapping antioxidative capacity (TRAC) of plasma was evaluated in samples from patients suffering from various inflammatory and autoimmune rheumatic diseases (n=104) and correlated with the phorbol ester-stimulated chemiluminescence (CL) of neutrophils and monocytes in unseparated blood. Plasma and blood samples from age- and sex-matched healthy volunteers (n=25) and from patients with non-rheumatic internal diseases (n=31) served as controls.

A 2 to 10 fold increase in whole blood chemiluminescence was found in rheumatic patients, which paralleled 50–80% decreased levels of plasma TRAC-values. While significant correlations between CL and TRAC were determined for patients with inflammatory arthritic diseases no correlations were found with patients suffering from connective tissue diseases. Prednisolone treatment of individual patients increased plasma TRAC-values substantially and decreased elevated levels of phagocytic CL generation to that of healthy controls.

The main potential application of the assays described here is for the convenient assessment of disease activity and progression in individual patients with rheumatic diseases.     

Characterization by human autoantibody of a nuclear antigen related to the cell cycle

Using a serum from a patient with an autoimmune disease, we have recently described a novel 55 000-dalton antigen (p55) in the nucleus of several animal cells including human ones. This antigen, designated PSL, was not related to the previously defined antigens recognized by sera from patients with systemic rheumatic diseases (Sm, n-RNP, SS-B, Scl-70). We have now found that p55 is associated with chromatin structures as it is released from the nucleus of mink cell fibroblasts by saline + DNase treatments. Analysis by sucrose gradient centrifugation of the nuclear material released in these conditions indicated that p55 co-migrated with core histones. Meanwhile, p55 was absent from the residual nuclear matrices (achromatinic nuclei). Localization of p55 in synchronized cells was performed by indirect immunofluorescence and immunoprecipitation. P55 appeared to accumulate in the nucleus during the S phase. Finally, it was not recognized by an anti-SV40 tumor serum that specifically precipitated the protein p53, which has been recently related to cell proliferation. Thus, PSL an p53, although apparently not antigenically related, appear to be implicated in the same step of the cell cycle.     

Monoclonal antibodies reactive with the T cell receptor zeta chain: production and characterization using a new method

We have developed a novel method for the production and characterization of monoclonal antibodies reactive with lineage-restricted intracellular Ag. Using this technique, we have produced a panel of antibodies that react specifically with permeabilized T lymphocytes but not with permeabilized B lymphocytes or native T cells. One of these antibodies, designated TIA-2, was found to react with greater than 98% of peripheral blood T lymphocytes. Immunoblotting experiments showed TIA-2 to recognize a 32 kd protein that was reduced to 16 kDa in the presence of 2-mercaptoethanol. Immunoprecipitates analyzed on non-reducing/reducing diagonal polyacrylamide gels showed the homodimeric structure recognized by TIA-2 to be associated with additional structures whose pattern closely resembled that of the T cell receptor complex. When immunoprecipitates formed using antibodies reactive with CD3 epsilon were immunoblotted with TIA-2, the homodimeric TCR zeta chain was specifically recognized. Using TIA-2 as a TCR zeta specific reagent, we show that whole cell expression of this TCR subunit is dramatically reduced following exposure to mAb reactive with CD3. mAb reactive with activating epitopes of CD2 were also capable of down-modulating the expression of TCR zeta, but to a lesser degree. Exposure to Con A or IL-2, on the other hand, did not reduce the whole cell expression of TCR zeta. Given the central importance of TCR zeta in the expression of a functionally competent Ag receptor, its reduced expression in response to certain activating stimuli is likely to play an important role in regulating T cell responsiveness.     

Reactivity of the human monoclonal antibody 33G2 with repeated sequences of three distinct Plasmodium falciparum antigens

The human mAb 33G2 has high capacity to inhibit in vitro invasion of erythrocytes by Plasmodium falciparum merozoites and, thus, is of special interest with regard to protective immunity against the parasite. In order to obtain more information about asexual blood stage Ag of P. falciparum that are seen by this antibody, material from synchronized P. falciparum cultures was studied by immunofluorescence, immunoelectron microscopy, and immunoblotting. Reactivity was mainly confined to the membrane of infected erythrocytes. Soon after merozoite invasion the antibody stained the erythrocyte membrane. This membrane-associated staining faded during intracellular development of the parasites. Beginning about 18 h after invasion, a dotted pattern appeared which increased in strength with time and persisted to schizont rupture. Pf155/RESA was the major Ag recognized in immunoblots of parasites collected throughout the entire erythrocytic cycle, although other polypeptides also bound the antibody. Among these was a 260-kDa polypeptide found in late trophozoites and schizonts. The specificity of the antibody was analyzed with synthetic peptides corresponding to repeated sequences in the P. falciparum Ag Pf155/RESA, Pf11.1, and Ag332. Synthetic peptides related to Ag332 were the most efficient inhibitors of antibody binding in immunofluorescence studies and cell ELISA. A beta-galactosidase-Ag332 fusion protein was also efficient in reversing reinvasion inhibition caused by 33G2. These results define a family of cross-reactive P. falciparum Ag recognized by mAb 33G2 and suggest that Ag332 was its original target.     

Effective antigen-specific immunotherapy in the marmoset model of multiple sclerosis

Mature T cells initially respond to Ag by activation and expansion, but high and repeated doses of Ag cause programmed cell death and can suppress T cell-mediated diseases in rodents. We evaluated repeated systemic Ag administration in a marmoset model of experimental allergic encephalomyelitis that closely resembles the human disease multiple sclerosis. We found that treatment with MP4, a chimeric, recombinant polypeptide containing human myelin basic protein and human proteolipid protein epitopes, prevented clinical symptoms and did not exacerbate disease. CNS lesions were also reduced as assessed in vivo by magnetic resonance imaging. Thus, specific Ag-directed therapy can be effective and nontoxic in primates.