Prominence of Pairing in Inclusive (p,2p) and (p,pn) Cross Sections from Neutron-Rich Nuclei

Fifty-five inclusive single nucleon-removal cross sections from medium mass neutron-rich nuclei impinging on a hydrogen target at ∼250  MeV/nucleon are measured at the RIKEN Radioactive Isotope Beam Factory. Systematically higher cross sections are found for proton removal from nuclei with an even number of protons as compared to odd-proton number projectiles for a given neutron separation energy. Neutron removal cross sections display no even-odd splitting, contrary to nuclear cascade model predictions. Both effects are understood through simple considerations of neutron separation energies and bound state level densities originating in pairing correlations in the daughter nuclei. These conclusions are supported by comparison with semimicroscopic model predictions, highlighting the enhanced role of low-lying level densities in nucleon-removal cross sections from loosely bound nuclei.

Staphylococcal enterotoxin B in vivo modulates both gamma interferon receptor expression and ligand-induced activation of signal transducer and activator of transcription 1 in T cells

Superantigens (SAg) are bacterial exotoxins that provoke extreme responses in the immune system; for example, the acute hyperactivation of SAg-reactive T cells that leads to toxic shock syndrome is followed within days by strong immunosuppression. The gamma interferon (IFN-gamma) response is deeply affected in both extremes. The implication of IFN-gamma in the pathophysiology of lethal shock induced in mice after a secondary challenge with the SAg staphylococcal enterotoxin B (SEB) prompted us to study the regulation of IFN-gamma secretion and the intracellular response. We demonstrate in this study that a rechallenge with SEB becomes lethal only when given inside a critical time window after SEB priming and is associated with an increase of IFN-gamma serum release 72 h after priming. However, at this time, a selective blockade of IFN-gamma/STAT1 signaling develops in spleen cells, correlating with a lack of expression of the IFN-gamma receptor beta subunit and STAT1 in the T-cell population. Selective blockade of the STAT1 signaling pathway--while simultaneously maintaining STAT3 signaling and expression--may be a protective mechanism that shortens IFN-gamma production during the Th1 effector response. This blockade may also have consequences on switching towards a suppressor phenotype with chronic exposure to the superantigen.

Activation-associated phenotype of CD3 T cells in acute graft-versus-host disease

During the effector phase of graft-versus-host disease (GvHD) response, donor T cells play an essential role and they are believed to change the expression of activation and co-stimulatory markers associated with functional alloreactivity. We analysed the expression of CD25, CD69, HLA-DR, CD154 and CD134 on CD4+ and CD8+ T cells by flow cytometry during acute GvHD (aGvHD) in 24 patients receiving human leucocyte antigen (HLA)-identical stem cell transplants. Expression of these molecules in nine patients with stages I-IV aGvHD was compared with 15 patients without aGvHD (n = 15). Serial analysis showed that peripheral blood of aGvHD patients presented a significant increase of CD4+ CD25+ cells (P < 0.03), CD4+ CD69+ (P < 0.04) and CD4+ CD134+ cells (P < 0.01). Additionally, there was a significant increase in CD8+ cells expressing CD134 (P = 0.007) and CD154 (P = 0.02). After resolution of aGvHD, the increased expression of these molecules returned to values comparable to patients without aGvHD. Only two of the 15 patients without clinical signs of aGvHD presented activated T cells that could not be attributed to development of aGvHD. In summary, our data show that multiple activation molecules are preferentially up-regulated on CD4+ and CD8+ T cells from patients with aGvHD. These patients had a significant increase in the expression of the co-stimulatory molecules CD134 and CD154.

Implication of STAT1 and STAT3 transcription factors in the response to superantigens

The activation of STAT1 and STAT3 in response to SEB was analyzed in spleen of Balb/c mice. The intraperitoneal injection of the superantigen SEB activated STAT1 and STAT3 in spleen. Activated STAT1 almost completely disappeared in 24 h even though activated STAT3 was present for more than 48 h after SEB injection. Cyclosporine A was able to block the initial STAT1 activation, but STAT3 activation was only partially affected. SEB also increased the mRNA levels for STAT1, STAT3 and SOCS1. When a second injection with SEB was given 72 h after the first stimulus, STAT1 activation was much lower than that observed after the first stimulation with SEB and no increase in the STAT1 mRNA level was observed. Nevertheless, after this second injection, STAT3 was again activated without any significant interference from the first stimulus and the STAT3 and SOCS1 mRNA levels again increased. These data indicate that a first stimulation with superantigen re-programs cells so that they respond to a second stimulation in a different way. Understanding the mechanisms implicated in this re-programming is basic for designing therapeutic strategies in processes such as septic shock.

DRB1*1446 allele variations in the group-specific annealing sites of common amplification primers

A cord blood unit from the Umbilical Cord Bank of Barcelona was initially typed by sequence-based typing (SBT) as DRB1* 0701. However, the subsequent confirmation by sequence-specific oligonucleotide probes (SSOP) revealed an unusual hybridization pattern that did not fit any of the known HLA-DRB1 alleles or allelic combinations. Molecular cloning and sequencing with primers located at introns 1 and 2 provided the definitive identification of a novel DRB1*1446 allele. It was similar to DRB1*1402 at exon 2 except for nucleotide substitutions at codons 10, 11 and 12 (from YST to LRK) that coincide with the 5'-end group specific site for the annealing of common amplification primers used by SBT and sequence-specific primers.

Identification of a novel HLA-DRB1 allele, DRB1*0108, by sequence-based DRB typing in two siblings

We report here a novel DRB1 allele identified during sequence-based HLA-DRB typing. This allele was detected during routine HLA typing of a patient and his family prior to bone marrow transplantation. The new allele, DRB1*0108, was found in the patient and in a brother. Molecular cloning and sequencing confirmed that the new DRB1 allele is identical to DRB1*0101 at exon 2 except for a single nucleotide substitution at codon 37 (TauCC-->TauAlphaC), changing the encoded serine to tyrosine. This position of the beta1 domain lies in the floor of the antigen-binding groove and shows the highest polymorphism among DRB1 alleles.

Familial CD8 deficiency due to a mutation in the CD8 alpha gene

CD8 glycoproteins play an important role in both the maturation and function of MHC class I-restricted T lymphocytes. A 25-year-old man, from a consanguineous family, with recurrent bacterial infections and total absence of CD8(+) cells, was studied. Ab deficiencies and ZAP-70 and TAP defects were ruled out. A missense mutation (gly90-->ser) in both alleles of the immunoglobulin domain of the CD8 alpha gene was shown to correlate with the absence of CD8 expression found in the patient and two sisters. Conversely, high percentages of CD4(-)CD8(-)TCR alpha beta(+) T cells were found in the three siblings. A novel autosomal recessive immunologic defect characterized by absence of CD8(+) cells is described. These findings may help to further understanding of the role of CD8 molecules in human immune response.

Antibodies against a novel nucleolar and cytoplasmic antigen (p105-p42) present in the sera of patients with a subset of rheumatoid arthritis (RA) with signs of scleroderma

We identified three patients (two of them relatives) with RA and signs of scleroderma whose sera contained a high titre of IgG class antibodies against the nucleoli and the nucleoplasm of cells of different mammalian origins. Sera from these patients uniformly immunoprecipitated four polypeptides, from a 35S-methionine-labelled HeLa cell extract, whose mol. wts were 120, 105, 95 and 42 kD. Of these, the 95-kD protein was highly phosphorylated. By immunoblotting, these sera reacted with 105-, 95- and 42-kD proteins and affinity-purified antibodies from these, demonstrating that 105- and 95-kD proteins shared cross-reactive epitopes. Moreover, affinity-purified antibodies from each of these proteins immunoprecipitated the whole complex. Localization studies using immunoelectron microscopy and in vivo actinomycin-D-treated cells demonstrated that the 105-, 95- and 42-kD proteins were present in the granular component of the nucleolus and the nucleoplasm. In addition, the 105- and 95-kD were present in free polyribosomes as well as ribosomes attached to endoplasmic reticulum. Pulse/chase experiments strongly suggested that the complex was accomplished shortly after a 10-min pulse. It was preferentially present in the nucleus after a 2 h chase and in both nucleus and cytoplasm after a 5 h chase. We conclude that a protein complex with a main nucleolar distribution is a new autoantigen (p105-p42) recognized by autoantibodies present in the serum of a subgroup of patients with RA and scleroderma signs. These antibodies could be useful as diagnostic markers and as tools for further studies involving the biology of the nucleolus.

Detection of anti-PL-12 autoantibodies by ELISA using a recombinant antigen; study of the immunoreactive region

Autoantibodies to aminoacyl-tRNA synthetases are highly associated with myositis and detection is important in clinical diagnosis; however, current methods of screening limit its clinical utility. In the present study, alanyl-tRNA synthetase (PL-12) recombinant protein was obtained by immunological screening of a HeLa expression library and used in an ELISA with 22 anti-PL-12 sera, 200 autoimmune sera negative for PL-12 and 100 healthy individual sera. Sensitivity of the method was 95% (21/22) and specificity 100%. Mapping of the immunoreactive region was carried out using three anti-PL-12 sera and different recombinant protein-derived peptides. Results show that the same conformational epitope located within amino acids 730-951 of the PL-12 antigen outside the catalytic region was recognized by the three anti-PL-12 sera tested. We conclude that ELISA using recombinant protein is an effective and useful method for routine screening for anti-PL-12 autoantibodies.

The two isoforms of the 90-kDalton nucleolus organizer region autoantigen (upstream binding factor) bind with different avidity to DNA modified by the antitumor drug cisplatin

It has been previously described that some proteins containing HMG boxes are able to bind more strongly to DNA modified with cis-diamminedichloroplatinum (II) (cisplatin) than to unmodified DNA. In the present study, we analyzed the interaction of cisplatin-modified DNA with the human autoantigen NOR-90 (UBF), a transcription factor that contains several HMG boxes. Using autoantibodies against NOR-90 to perform ELISA and immunoprecipitation, it was confirmed that NOR-90 (UBF) was able to bind cisplatin-modified DNA more avidly than unmodified DNA or trans-diamminedichloroplatinum(II) (transplatin) modified DNA. Moreover, by Southwestern, we observed that the 97 kDalton isoform of NOR-90 (UBF1) was able to bind cisplatin-modified DNA more strongly than the 94 kDalton isoform (UBF2); binding of unmodified DNA or transplatin-modified DNA was not detected with either isoform. Sera containing autoantibodies against NOR-90 did not inhibit, but increased the binding of NOR-90 to cisplatin-modified DNA.

Stat1 implication in the immune response to superantigens in vivo

We analyzed the activation and changes in the protein level of STAT1 as a consequence of in vivo treatment with superantigens. Ninety minutes after i.p. injection of the staphylococcal enterotoxin B (SEB), a complex containing STAT1 that was able to specifically bind to DNA containing GAS-like sequences was activated in mouse splenocytes. This complex had the same characteristics as that induced by IFN-gamma in several in vitro systems. Activation of the complex was inhibited by cyclosporin A, and Abs against IFN-gamma severely decreased the amount of complex detected. When splenocytes were analyzed 24 h after SEB treatment, a high increase in the amount of the STAT1 isoforms, STAT91 and STAT84, was observed by Western analysis, but binding to GAS-like sequences was clearly decreased when compared with analysis at 90 min. Nevertheless, when SEB was injected a second time 24 h after the first injection, the binding of STAT1 to GAS-like sequences had risen again. This approach corroborates the implication of IFN-gamma in the response to superantigens in vivo and shows the relevance of analysis of transcription factors in defining the molecular events involved in the immune response.

Stat1 implication in the immune response to superantigens in vivo

We analyzed the activation and changes in the protein level of STAT1 as a consequence of in vivo treatment with superantigens. Ninety minutes after i.p. injection of the staphylococcal enterotoxin B (SEB), a complex containing STAT1 that was able to specifically bind to DNA containing GAS-like sequences was activated in mouse splenocytes. This complex had the same characteristics as that induced by IFN-gamma in several in vitro systems. Activation of the complex was inhibited by cyclosporin A, and Abs against IFN-gamma severely decreased the amount of complex detected. When splenocytes were analyzed 24 h after SEB treatment, a high increase in the amount of the STAT1 isoforms, STAT91 and STAT84, was observed by Western analysis, but binding to GAS-like sequences was clearly decreased when compared with analysis at 90 min. Nevertheless, when SEB was injected a second time 24 h after the first injection, the binding of STAT1 to GAS-like sequences had risen again. This approach corroborates the implication of IFN-gamma in the response to superantigens in vivo and shows the relevance of analysis of transcription factors in defining the molecular events involved in the immune response.

Autoantibodies against a novel DNA-binding protein: DNA-protein interaction as a requisite for expression of antigenic reactivity

A novel DNA-binding protein complex, the HB complex, has been characterized by means of autoantibodies. Three proteins of 9000, 7500, and 7000 Da constitute the HB complex. The 9000- and 7500-Da proteins are phosphorylated. Autoantibodies recognize the 7000-Da protein when it is bound to DNA. No reactivity against any protein was observed when the complex was dissociated from DNA. The three proteins are acidic (pI 5-6.2), and the complex was able to bind to synthetic double-stranded DNAs of different composition.

Autoantibodies to a transfer RNA-associated protein in a murine model of chronic graft versus host disease

We established chronic graft vs host disease (GVHD) in (C57BL/10 x DBA/2)F1 mice with an injection of lymphoid cells from the parental DBA/2 strain. In addition to Abs earlier reported, of the 20 animals studied 13 developed Abs against transfer RNA/protein particles. Ten of the 13 sera immunoprecipitated a similar-sized RNA that co-migrated in PAGE with isoleucine tRNA. In immunoblots against proteins affinity purified using anti-isoleucyl-tRNA synthetase prototype serum, 7 of the 10 sera reacted with a polypeptide of 76 kDa that was similar in size to a protein recognized by a human anti-isoleucyl-tRNA synthetase serum. Three of 10 sera significantly and specifically inhibited isoleucyl-tRNA synthetase enzyme activity and one inhibited lysyl-tRNA synthetase activity. These data suggest that the autoantibodies to tRNA-associated proteins that develop in GVHD mice may react with amino acyl-tRNA synthetases, particularly those belonging to the multienzyme complex. Such autoantibodies are associated with myositis in humans, and these mice showed evidence compatible with myositis that appeared to be a manifestation of their GVHD. No previous example of spontaneous development of antisynthetases in animals has been described. We also demonstrated the presence of Abs against the NOR:90 nucleolar Ag as a new target in chronic GVHD. We conclude that chronic GVHD in mice provides a model for the study of the autoimmune responses that characterize human diseases such as mixed connective tissue disease, scleroderma, SLE, and myositis with a wider autoantibody response than that described so far.

Autoantibodies to a transfer RNA-associated protein in a murine model of chronic graft versus host disease

We established chronic graft vs host disease (GVHD) in (C57BL/10 x DBA/2)F1 mice with an injection of lymphoid cells from the parental DBA/2 strain. In addition to Abs earlier reported, of the 20 animals studied 13 developed Abs against transfer RNA/protein particles. Ten of the 13 sera immunoprecipitated a similar-sized RNA that co-migrated in PAGE with isoleucine tRNA. In immunoblots against proteins affinity purified using anti-isoleucyl-tRNA synthetase prototype serum, 7 of the 10 sera reacted with a polypeptide of 76 kDa that was similar in size to a protein recognized by a human anti-isoleucyl-tRNA synthetase serum. Three of 10 sera significantly and specifically inhibited isoleucyl-tRNA synthetase enzyme activity and one inhibited lysyl-tRNA synthetase activity. These data suggest that the autoantibodies to tRNA-associated proteins that develop in GVHD mice may react with amino acyl-tRNA synthetases, particularly those belonging to the multienzyme complex. Such autoantibodies are associated with myositis in humans, and these mice showed evidence compatible with myositis that appeared to be a manifestation of their GVHD. No previous example of spontaneous development of antisynthetases in animals has been described. We also demonstrated the presence of Abs against the NOR:90 nucleolar Ag as a new target in chronic GVHD. We conclude that chronic GVHD in mice provides a model for the study of the autoimmune responses that characterize human diseases such as mixed connective tissue disease, scleroderma, SLE, and myositis with a wider autoantibody response than that described so far.

Autoantibodies against a serine tRNA-protein complex implicated in cotranslational selenocysteine insertion

We describe an autoantibody specificity present in a subgroup of patients with a severe form of autoimmune chronic active hepatitis. These antibodies precipitate a 90-nucleotide RNA from human whole cell extracts and recognize a 48-kDa polypeptide in immunoblotting assays. The RNA is a UGA suppressor serine tRNA that carries selenocysteine (tRNA[Ser]Sec)), as shown by sequence analysis. The protein does not appear to be seryl-tRNA synthetase; rather, it is an excellent candidate for a factor involved in cotranslational selenocysteine incorporation in human cells.

Different strains of donor parental lymphoid cells induce different models of chronic graft-versus-host disease in murine (Balb/c x A/J)F1 hybrid hosts

The induction of a chronic graft-versus-host (cGVH) disease in (Balb/c x A/J)F1 mice by the intravenous injection of either Balb/c or A/J parental lymphoid cells led to the development of two different models of disease. In this paper we compared the clinical aspects and the antigen specificities which recognized the autoantibodies developed by the animals of these two models of cGVH disease. Renal disease, alopecia, and purpura lesions were common in both models, although their frequency and intensity varied between groups. The models were differentiated by two main characteristics. When donor cells were of Balb/c origin, a joint disease similar to rheumatoid arthritis developed in 50% of the animals, and when donor cells were of A/J origin, 25% of the animals developed edema of the front feet, occasionally with loss of the nails, similar to that of scleroderma. Differences among the autoantibodies found in the sera of these two groups of mice were also observed. After the injection of Balb/c lymphoid cells, rheumatoid factors reactive with human and murine IgG were characteristically present (69 and 75%, respectively) and a statistically significant correlation was found between high titers of rheumatoid factor and arthritis (P less than 0.001). Antinuclear antibodies (ANAs) were present in all animals. Anti-dsDNA and anti-histones were positive in 50 and 25%, respectively. Anti-snRNP were detected at a low titer in 35% of the animals. When donor cells were of A/J origin, ANAs were also present in all mice. Anti-dsDNA, anti-histones, and anti-snRNPs antibodies were present in 90, 15, and 65%, respectively. The most outstanding characteristics among anti-snRNPs were the high titers of anti-U1 and anti-U3 detected in 50 and 30%, respectively. Rheumatoid factors reactive with human and murine IgG were positive in 15 and 42% of animals, respectively, but no significant correlation was found between these factors and disease. Our results indicate that the graft-versus-host disease induced in the same F1 strain of mice can be manifested in different forms of connective tissue disease, depending on whether the cells come from one or the other of the parental strains. Furthermore, in this paper the occurrence of rheumatoid factors in mice with cGVH is described for the first time.

Identification of protein components reactive with anti-PM/Scl autoantibodies

The PM/Scl antigen from mammalian cells has been characterized as a nucleolar and nucleoplasmic molecular complex containing at least 16 polypeptides ranging in molecular weight from 110 to 20 kD. Of these polypeptides, we have found those of 68, 39 and 20 kD to be in a phosphorilated form. Whereas the entire complex was precipitated by all the anti-PM/Scl sera tested, in immunoblots the antibodies specifically recognized determinants on the 110-kD protein. This protein was immunoprecipitated more preferentially from nucleoli extracts than from total cell extracts. Moreover, this protein disappeared from the immunoprecipitates when treated with DNAse. Likewise, the immunoblot reaction of the specific antibodies with the 110-kD protein was abolished by treatment of the extracts with DNAse and trypsin, and was resistant when extracts were treated with RNAse. Affinity-purified antibodies from this protein selectively stained the nucleoli and the nucleoplasm of the mammalian cells. Moreover, when the cultured cells used in immunofluorescence were treated with DNAse, the affinity purified antibodies from the 110-kD protein gave negative fluorescence. However, when whole anti-PM/Scl sera were used, a nucleolar and nucleoplasmic staining was found. We conclude that the 110-kD protein has at least one of the autoimmunogenic epitopes of the PM/Scl antigen, recognized by all anti-PM/Scl sera tested. Other epitopes differing in their DNAse sensitivity may also be present in the PM/Scl antigen.

Murine graft vs host disease. A model for study of mechanisms that generate autoantibodies to ribonucleoproteins

We established chronic graft vs host disease in (BALB/c x A/J) F1 mice with the injection of lymphoid cells from the parental A/J strain. These animals developed glomerulonephritis, forefoot edema, alopecia, splenomegaly, and lymphadenopathy to various degrees, and all developed antinuclear antibodies. To determine whether these antibodies were directed against the small nuclear ribonucleoprotein (snRNP) particles that are characteristic targets for autoimmune responses in human rheumatic diseases, sera were studied in the 32P immunoprecipitation and immunoblotting assays. Among 20 mice, antibodies to snRNP developed in 10. These antibodies usually reached maximal levels about 4 wk after induction of graft vs host disease and generally fell thereafter. However, two mice developed antibodies to snRNP between the 10th and 20th wk of follow-up. Sera from six mice strongly recognized the U1 snRNP and an additional serum strongly bound both the U1 and U3 particles. Several sera contained lower levels of antibodies specific for the U3 and possibly pre-U2 snRNP particles. In immunoblots, sera that immunoprecipitated the U1 snRNP bound epitopes located on its 70,000 Da, A, B'/B, and/or C polypeptides. Sera that immunoprecipitated the U3 snRNP recognized a 34,000-Da polypeptide. These polypeptides are known to bear the autoantigenic epitopes that are recognized by human sera containing anti-U1 RNP and anti-U3 RNP autoantibodies. We conclude that chronic graft vs host disease in mice provides a model for the study of the autoimmune responses that characterize human diseases such as mixed connective tissue disease, scleroderma, and SLE.

Murine graft vs host disease. A model for study of mechanisms that generate autoantibodies to ribonucleoproteins

We established chronic graft vs host disease in (BALB/c x A/J) F1 mice with the injection of lymphoid cells from the parental A/J strain. These animals developed glomerulonephritis, forefoot edema, alopecia, splenomegaly, and lymphadenopathy to various degrees, and all developed antinuclear antibodies. To determine whether these antibodies were directed against the small nuclear ribonucleoprotein (snRNP) particles that are characteristic targets for autoimmune responses in human rheumatic diseases, sera were studied in the 32P immunoprecipitation and immunoblotting assays. Among 20 mice, antibodies to snRNP developed in 10. These antibodies usually reached maximal levels about 4 wk after induction of graft vs host disease and generally fell thereafter. However, two mice developed antibodies to snRNP between the 10th and 20th wk of follow-up. Sera from six mice strongly recognized the U1 snRNP and an additional serum strongly bound both the U1 and U3 particles. Several sera contained lower levels of antibodies specific for the U3 and possibly pre-U2 snRNP particles. In immunoblots, sera that immunoprecipitated the U1 snRNP bound epitopes located on its 70,000 Da, A, B'/B, and/or C polypeptides. Sera that immunoprecipitated the U3 snRNP recognized a 34,000-Da polypeptide. These polypeptides are known to bear the autoantigenic epitopes that are recognized by human sera containing anti-U1 RNP and anti-U3 RNP autoantibodies. We conclude that chronic graft vs host disease in mice provides a model for the study of the autoimmune responses that characterize human diseases such as mixed connective tissue disease, scleroderma, and SLE.

Purification of hnRNP from HeLa cells with a monoclonal antibody and its application in ELISA: detection of autoantibodies

HnRNP antigen from HeLa cells was purified using a monoclonal antibody (383 IgM) that recognizes heterogeneous nuclear ribonucleoprotein (hnRNP). From extracts of HeLa cells radiolabelled with 32P, this antibody immunoprecipitates relatively large RNAs of heterogeneous size which are synthesized in the presence of actinomycin D at doses which suppress synthesis of ribosomal RNAs (characteristic features of heterogeneous nuclear RNA). In immunoblots, 383 IgM binds to seven polypeptides: one of approximately 23,000 daltons, three between 30,000 and 43,000 daltons which correspond to the known hnRNP polypeptides called A1, A2 and C1, one of approximately 50,000 daltons, and a doublet of approximately 120,000 daltons. These proteins comigrate through sucrose density gradients suggesting that they are physically associated. Thus, 383 IgM appears to define an epitope that is shared among a number of the protein components of hnRNP. This antibody has been used to design a simple and fast protocol which allows the determination of autoantibodies from human sera by ELISA.

Anti-NOR 90. A new autoantibody in scleroderma that recognizes a 90-kDa component of the nucleolus-organizing region of chromatin

We identified a patient (CAG) with scleroderma whose serum contained a high titer of IgG class antibodies that stained nucleoli in a pattern of independent tiny spots. When tested on isolated chromosomes, these antibodies selectively stained the nucleolus-organizing regions (NOR) of chromosomes 13, 14, 15, 21, and 22. These staining patterns were not altered when substrate cells and chromosomes were treated with RNase, 0.1 M HC1, or 4 M urea, but they were abolished by treatment with DNase and trypsin. Immunoblots performed with serum CAG on isolated nucleolar substrates identified a protein antigen of approximately 90 kDa. Antibodies affinity-purified from this protein selectively stained nucleoli and NOR chromosomal regions. Therefore, this protein is the antigen that accounts for the ability of serum CAG to recognize the NOR. In a search for the NOR 90-kDa specificity among 254 patients with various rheumatic diseases, we found nine additional patients whose sera stained metaphase chromosomes selectively at the NOR. Sera from five of them (three with scleroderma, two of unknown diagnosis) recognized a protein that electrophoretically co-migrated with the CAG antigen. Thus, scleroderma is present in at least four of six who appear to have this specificity. We conclude that autoantibodies to the NOR 90-kDa antigen have an association with scleroderma and may be useful diagnostically and as a probe for further studies of the biology of the cell nucleolus.

Anti-NOR 90. A new autoantibody in scleroderma that recognizes a 90-kDa component of the nucleolus-organizing region of chromatin

We identified a patient (CAG) with scleroderma whose serum contained a high titer of IgG class antibodies that stained nucleoli in a pattern of independent tiny spots. When tested on isolated chromosomes, these antibodies selectively stained the nucleolus-organizing regions (NOR) of chromosomes 13, 14, 15, 21, and 22. These staining patterns were not altered when substrate cells and chromosomes were treated with RNase, 0.1 M HC1, or 4 M urea, but they were abolished by treatment with DNase and trypsin. Immunoblots performed with serum CAG on isolated nucleolar substrates identified a protein antigen of approximately 90 kDa. Antibodies affinity-purified from this protein selectively stained nucleoli and NOR chromosomal regions. Therefore, this protein is the antigen that accounts for the ability of serum CAG to recognize the NOR. In a search for the NOR 90-kDa specificity among 254 patients with various rheumatic diseases, we found nine additional patients whose sera stained metaphase chromosomes selectively at the NOR. Sera from five of them (three with scleroderma, two of unknown diagnosis) recognized a protein that electrophoretically co-migrated with the CAG antigen. Thus, scleroderma is present in at least four of six who appear to have this specificity. We conclude that autoantibodies to the NOR 90-kDa antigen have an association with scleroderma and may be useful diagnostically and as a probe for further studies of the biology of the cell nucleolus.