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About 50% of patients with the polymyositis/scleroderma (PM-Scl) overlap syndrome are reported to have autoantibodies to a nuclear/nucleolar particle termed PM-Scl. The particle is composed of several polypeptides of which two have been identified as autoantigens. In this report, human cDNA clone coding for the entire 75-kD autoantigen of the PM-Scl particle (PM-Scl 75) was isolated from a MOLT-4 lambda gt-11 library. The deduced amino acid sequence of the cDNA clone represented a protein of 355 amino acids and 39.2 kD; the in vitro translation product of this cDNA migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) at approximately 70 kD. The aberrant migration of the polypeptide in SDS-PAGE was shown to be related to the COOH half that was rich in acidic residues. Authenticity of the cDNA coding for PM-Scl 75 was shown by immunoreactivity of PM-Scl sera with in vitro translation products and recombinant fusion proteins encoded by the cDNA. In addition, rabbit antibodies raised to recombinant fusion protein reacted in immunofluorescence, immunoblotting, and immunoprecipitation with the characteristic features displayed by human anti-PM-Scl sera.

Using a post-embedding immunogold labeling procedure, we found that monoclonal antibody against A (MAb-A) or B antigen (MAb-B) reacted with nuclear heterochromatin regions, as well as secretory granules, in mucous cells of human cervical glands. Systematic and critical observation of specimens from 24 individuals of different blood groups revealed that the labeling pattern with MAb with strictly dependent on the blood group (A,B, or O) of the donors, i.e., MAb-A reacted with the heterochromatin from blood group A and AB but not with B and O individuals. Labeling with MAb-B was also specific for the heterochromatin from blood group B donors. On the other hand, MAb against H antigen did not react with the heterochromatin from any individuals examined, despite the fact that H antigens were detected by the MAb in secretory granules. Such specific reactions provide evidence that certain types of blood group-related antigens exist in the nuclear heterochromatin in mucous cells of human cervical glands. In contrast to the secretory granules in which ABH antigens were recognized by blood group-specific lectin, heterochromatin regions had little or no affinity for these lectins. Furthermore, the secretory status of individuals affected the staining intensity with MAb in secretory granules but not in the heterochromatin. These results suggest that the blood group substances found in the heterochromatin may have different molecular properties from those in the secretory granules, although both have the same determinant structures of ABH antigens.

Indirect immunofluorescence(IIF) and double immunodiffusion (DID) were performed on the sera of 64 patients who had a nucleolar immunofluorescence pattern on HEp-2 cells. Forty-nine of the sera were from 296 patients with systemic scleroderma (SSc) and 15 sera were from 214 patients with systemic lupus erythematosus (SLE). A homogeneous nucleolar staining pattern was found in 45 of the 64 sera (70.3%), a clumpy fluorescence associated with fibrillarin antibody in 14 (21.8%) and a speckled pattern was found in five of the sera (7.8%). There was a clear correlation between the sera which showed a homogeneous nucleolar staining pattern with symptoms of the polymyositis/scleroderma overlap syndrome that differed from SSc with concomitant myositis. The clumpy pattern was mainly associated with diffuse scleroderma and the speckled pattern with limited scleroderma (previously called acrosclerosis).

With the scleroderma autoantinucleolar antiserum which was discribed in our previous paper, we identified a novel group of nucleolar organizer associating proteins, ANOP. By means of immunoblotting, it was found that ANOP mainly consists of three polypeptides with molecular weights of 65, 76, and 78 KD respectively. Immunoelectron microscopy demonstrated that ANOP is localized in the shells of dense fibril components surrounding fibrillar centers of nucleolus. Moreover, indirect immunofluorescence studies on various cells of vertebrate animals indicated that ANOP is a group of highly conserved nucleolar antigens. The fibrillar centers of human, mouse, chinese hamster, chicken, frog and crucian carp cells can all be brightly stained by ANOP specific antiserum. However, it was found that in amphibian, the erythrocytes and the early embryo cells prior to gastrulation are devoid of ANOP. During gastrulation, ANOP begins to appear in the nuclei, and then, the content of ANOP in nucleoli apparently increases gradually. These phenomena suggest that ANOP may take a role in rRNA gene activity.

Sera from 32 bone marrow allograft recipients were screened for the presence of autoantibodies 4-61 months post-graft. Sera from 12 of 19 patients with extensive chronic graft-versus-host disease (c-GVHD) stained the nucleolar region strongly in immunofluorescence, indicating the presence of specific antinucleolar antibodies. In contrast, none of three patients with limited and none of 10 patients without c-GVHD had antinucleolar antibodies. Antibodies reacting with nuclear constituents other than nucleoli were found in five of the 12 antinucleolar positive patients. The appearance of antinucleolar antibodies coincided with early clinical symptoms of c-GVHD. We conclude that the appearance of antinucleolar antibodies after bone marrow transplantation is specific for patients with extensive c-GVHD. Furthermore, the development of extensive c-GVHD is paralleled by the emergence of these antinucleolar antibodies.

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.

The gene encoding the hepatitis delta virus structural antigen (HDAg) was linked to a neomycin resistance gene in a retrovirus expression vector, and human HepG2 cells were transfected with the recombinant plasmid. A stable cell line was cloned that expressed HDAg in the nuclei of 100% of cells, in a pattern indicating a close relationship with cell nucleoli. Analysis of partially purified recombinant HDAg by HPLC showed an Mr in the range of 7 x 10(5) to 2 x 10(6), which appeared to contain conformation-dependent epitopes, whereas the density of the antigen was 1.19 g/ml by equilibrium centrifugation in caesium chloride, and in rate zonal centrifugation it sedimented with a value of 50S, close to that of particulate hepatitis B virus surface antigen. Immunoblotting demonstrated a single polypeptide with an Mr of 24K which corresponded to the smaller of the two HDAg-specific polypeptides present in infected sera. The recombinant HDAg polypeptide was shown to be a RNA-binding protein with specificity for both genomic and antigenomic species of hepatitis delta virus RNA.

Two cis-acting elements in the p120 gene play important roles in transcription; the region from -537 to -278 is necessary for initiation of transcription, and the region from -1426 to -1223 is necessary for efficient transcription. The distal element(s) which lies upstream of -278 is required for initiation of transcription.

Several nucleolar antigens are defined by human autoantibodies. These antigens can therefore be used to follow the fate of nucleolar components through mitosis when this major nuclear structure disintegrates and becomes reassembled in G1-phase. We found that fibrillarin leaves the nucleolus before complete breakdown of this structure and attaches to chromosomes before nuclear envelope breakdown. In mouse, fibrillarin attaches over the chromosomal surface except for the excluded centromeric region. The antigen is transported to the new nucleus via the chromosomes and is last seen on chromosomal surfaces facing the cytoplasm during nuclear envelope reformation. Lamin B reappears on the same chromosomal surfaces before the nucleolar antigen is removed and aggregates for new nucleolar reformation in G1-phase cells. From our observations, we postulate that the antigen acts in concert with other proteins as a nuclear envelope equivalent by forming a protective sheath around the chromosome, that it excludes larger molecules, and helps to separate the chromosomes, in addition to segregation of the ribonucleoprotein (RNP) back to the nucleus for nucleolar reconstruction. We also suggest that the selective retention of these antigens from certain areas on individual chromosomes together with specific lamin B attachment over these chromosomal surfaces allows for a nonrandom positioning of chromosomes in the nucleus.

A non-histone protein with mol. wt of 48,000 differentially expressed in normal and tumour cells was identified using immunological criteria. Antibodies were raised against a component specific for Kirkman-Robbins hepatoma of mol. wt about 48,000 separated from hepatoma non-histone proteins by preparative electrophoresis in polyacrylamide gel. It was demonstrated by immunoblotting that Morris hepatoma 7777 and Ehrlich ascites cells share an antigenic non-histone protein with Kirman-Robbins hepatoma. Tumour cells when compared with normal cells, i.e. hamster and rat liver, are characterized by significant enrichment of this component. Intracellular distribution of the polypeptide with mol. wt 48,000 suggests that this component may be a structural protein the biosynthesis of which increases or the antigenic determinants of which change in tumour cells.

The aim of this study was to investigate the use of a nucleolar antigen to discriminate between proliferating and resting cells. Antinucleolar antibodies (Si87) were obtained from a scleroderma patient. The specificity of immunostaining was verified and morphological changes in nucleoli were monitored using a fluorescence microscope. Fluorescence of propidium iodide-stained DNA and nucleolar immunofluorescence were measured by flow cytometry. Following phytohaemagglutinin stimulation the number of nucleoli of normal human peripheral blood lymphocytes increased about 3-fold, accompanied by enlargement of nucleolar size. Simultaneously a mean increase in total immunofluorescence per cell by a factor of three was detected. The method developed and applied here allows a discrimination between resting and proliferating human lymphocytes on the basis of their nucleolar antigen content.

One of the most characteristic serologic features of systemic sclerosis (scleroderma) is the occurrence of autoantibodies against nuclear and most notably against nucleolar antigens. This humoral autoimmune response is one of best studied immunologic phenomena in scleroderma. Detailed molecular information on the structure and function, as well as on reactive epitopes of autoantigens targeted by specific serum antibodies, has been revealed by clinical, immunologic, and biochemic studies in several laboratories. Autoantigens such as DNA topoisomerase I (Scl-70), centromere proteins, RNA polymerase I, U3 RNP-associated fibrillarin, PM-Scl, and 7-2 RNP antigens were shown to be specific targets of scleroderma patients and were observed to have clinical correlates within the scleroderma disease spectrum. Therefore, autoantibodies in scleroderma are not only valuable diagnostic tools but also prognosticators of the disease. Although autoantibodies in scleroderma do not appear to play a pathogenetic role in the disease process, the knowledge of the structure and function of their reactive antigens may help in answering questions concerning the etiology of the disease.

Reexamination of ANA positive sera with nucleolare fluorescence staining on HEp-2 cells and hamster liver imprints revealed 3 sera with an uniform characteristic pattern. It is characterized by: 1. Strong clumpy fluorescence of nucleoli in the interphase. 2. Missing nucleoplasma staining (pure nucleolar). 3. Characteristic granular staining of the cytoplasma from the condensed chromosoma in mitosis. 4. Additive fluorescence of a nucleolus-like body. 5. Extremely high antibody titers. 6. Negative immunodiffusion. This nucleolar staining pattern was described by Bernstein et al. as a clumpy nucleolar pattern. It is produced through an antibody to the dense fibrillar component of the nucleolus (fibrillarin). This antigen is a protein of the U3 RNP with a molecular weight 34 kDa. Clinically is the fibrillarin antibody highly specific for systemic scleroderma especially with diffuse skin involvement. We found it in 1% of scleroderma patients. Its pathogenetic importance is not known.

Sera of patients with rheumatic diseases often contain autoantibodies to nuclear antigens. Problems of the specificity of autoantibodies and of their usage for studying nuclear components and of the whole nuclear organization are reviewed.

A new protein antigen of the nucleolus organizer region (NOR), designated He, was recognized by human autoantibodies obtained from a patient with Raynaud phenomenon. In mitotic cells of all vertebrate species tested. He serum selectively immunostained the chromosomal NORs. A completely unexpected characteristic of the He antigen was its location during interphase. In mammalian cell substrates, it was concentrated in numerous nucleoplasmic granules, with minor amounts of the antigen uniformly distributed throughout the entire nucleus. In interphase nuclei of lower vertebrate cells, however, the antigen was preferentially located in the nucleolus. The antigenicity of He is not dependent on RNA or DNA; its cytochemical properties operationally classify it as a nonhistone component of the chromosome scaffold. The He antigen was present in the residual nucleolar structures of cells that were not at all active in rRNA synthesis, such as mammalian late spermatids and amphibian erythrocytes.

A panel of sera derived from 138 patients with primary bronchogenic carcinoma, non-neoplastic lung conditions and from blood donors was tested for presence of autoantibodies by indirect immunofluorescence on fixed cells of established lung cancer cell line and lung fibroblasts as a substrate. Autoantibodies were detected in 87% and 64% out of patient sera respectively and in 9% of donor sera. Immunofluorescence patterns permitted to distinguish 3 antibody specificities: anti-nucleolar, anti-cytoplasmic and anti-nuclear ones. The major differences were noted in incidence of anti-nucleolar antibodies, which were present in 77% of lung cancer patients and only in 14% of patients with non-neoplastic lung conditions. The autoantibodies in question belonged to IgG and to lesser degree IgA class of immunoglobulin and were not apparently cancer specific because absorption with normal tissue homogenates removed their activity.

Sera from 7 patients with localized and 35 with systemic scleroderma were studied for the presence of fluorescent antinuclear antibodies (FANA) (by indirect immunofluorescence on HEp-2 cells) and antibodies to extractable nuclear antigens (anti-ENA) (by immunodiffusion - ID - and counterimmunoelectrophoresis - CIE). In localized disease, antinuclear autoimmunity was limited to 1 FANA positive serum (14%); in systemic disease, the prevalence of FANA was 94% and that of anti-ENA ranged from 29% to 49% (by ID and CIE, respectively). The commonest ENA system, Scl-70, could be easily detected by CIE, in spite of the reported basic nature of the antigen. The anticentromere antibody occurred only in patients with acrosclerosis (7/26-27%), whereas the association of nucleolar + homogeneous FANA, as well as the anti-Scl-70, were found more frequently in diffuse scleroderma (9/9-100% and 6/9-67%, respectively). The presence of the anticentromere antibody excluded that of any anti-ENA, while a close association was found between nucleolar + homogeneous FANA and the anti-Scl-70. Pulmonary involvement was significantly more frequent in nucleolar + homogeneous FANA positive patients; moreover, in two cases the same pattern proved to predict the development of diffuse scleroderma.

By using both direct and indirect immunofluorescence technics and the PAP method, the authors observed an unusual immunocytochemical staining pattern in myeloma cells producing IgG 1(lambda). J chains were localized mainly as intranuclear spots, compared with gamma and lambda chains that are diffusely distributed in the cytoplasm with dense perinuclear accumulation. The present findings on the location, size, and number of the intranuclear spots suggest that J chains are nucleolus associated. The authors hypothesize that J chains are synthesized in the cytoplasm and transported into the nucleolus, where they associate with nucleolar proteins, or that they are synthesized within the nucleolus, which participates in biogenesis of ribosomes.

Antinucleolar antibody (ANoAb) was tested for in sera from 25 patients with systemic lupus erythematosus (SLE), 61 with progressive systemic sclerosis (PSS), 22 with chronic active hepatitis (CAH) and 28 healthy persons, using immunofluorescence reactivity with acetone-fixed monolayers of cultured human fibroblasts, and a procedure to reveal ANoAb when other antinuclear antibodies were concurrently present. ANoAb was found on direct testing in sera from 6 patients with SLE, 15 with PSS and 7 with CAH, but not in any of 28 sera from healthy persons; homogeneously reactive antinuclear antibody was also present in the serum of these 6 cases of SLE, in 6 of the 15 with PSS and in 3 of the 7 with CAH and, in SLE specifically, pre-treatment of fibroblast monolayers with DNase "unmasked" the presence of ANoAb in a further 7 sera which had shown only homogeneous nuclear staining in fibroblasts. ANoAb belonged to the IgG, IgM and IgA class in sera from cases of SLE and PSS, and to only the IgG and IgM class in sera from cases of CAH. ANoAb titres were highest in patients with PSS. ANoAb were sensitive to RNase in 5 cases, to RNase and DNase in 6, and were sensitive to combinations of RNase, DNase, NaC1, and trypsin in the remaining cases. We conclude that (i) fibroblast monolayers are a suitable substrate for the demonstration of ANoAb, (ii) homogeneous staining of cell nuclei may mask ANoAb, so that the incidence of ANoAb becomes higher in SLE than in PSS, (iii) low-titre ANoAb in CAH not visualized in frozen tissue sections may be detected on fibroblast monolayers, and (iv) nucleolar antigens probably include RNA, RNA bound to DNA, and RNA bound to proteins.

The present study was designed to characterize the human tumor nucleolar antigens found first in the HeLa cells and subsequently in a broad range of human cancers. For visualization of the antigens, HeLa cell nucleolar or nuclear protein fractions were analyzed on 4% polyacrylamide isoelectric focusing gels. The gels were incubated with rabbit antisera to HeLa cell nucleoli and then with fluorescein- or peroxidase-conjugated goat anti-rabbit immunoglobulin G. With this technique, two major nucleolar antigens (focusing at pH 6.3 and pH 6.1) were identified. These antigens were also found in the Namalwa cell, but not in human liver cells. Purification of the antigen(s) was achieved by selective extraction of Namalwa cell nuclei with 10 mM Tris-HCl (pH 8), 40 to 100% ammonium sulfate precipitation, diethylaminoethyl cellulose chromatography in which the antigen was eluted with 0.15 M NaCl buffer (DE-0.15M fraction), and use of isoelectric focusing gels. The immunostained bands (HuAg 6.3 and HuAg 6.1) and the bright nucleolar immunofluorescence of the HeLa cells were not observed after the antisera were preabsorbed with the DE-0.15M fraction. The immunostained bands (HuAg 6.3 and HuAg 6.1) and the nucleolar immunofluorescence of the HeLa cells were also observed when isoelectric focusing gels were incubated with antiserum from rabbits immunized with the DE-0.15M fraction. On the sodium dodecyl sulfate second dimension of the two-dimensional polyacrylamide gel electrophoresis, the antigen(s) migrated as single spots with appraent molecular weights of 54,000.

The antigenic phenotypes of several temperature-sensitive mutants of simian virus 40 were determined by an immunofluorescence microtechnique that allowed a very high degree of internal control for the conditions of virus infection and antigenic staining. The tumor (T), U, capsid protein (C), and virion (V) antigens were investigated. Productive infection in monkey cells and abortive infection in mouse cells were simultaneously monitored for antigen production at both permissive and restrictive temperatures. Complementation analyses of the mutants demonstrated two complementing groups (A and B) and one noncomplementing group ((*)). One of the complementing groups could be subdivided into two subgroups having very different antigenic phenotypes. The following phenotypes were observed at the restrictive temperature in monkey cells. (i) The noncomplementing group produced none of the antigens. (ii) Group A induced T antigen in moderately but consistently reduced numbers of cells. Other antigens were markedly reduced or absent. (iii) Some of the group B mutants produced T antigen but little or no U and V antigens. The C antigen appeared in the nucleolus and cytoplasm of this subgroup. (iv) In the other group B mutants, antigen synthesis was not altered. Similar phenotypes were observed in mouse cells, except that U, C, and V antigens could not be detected during either the mutant or wild-type virus infections at any temperature.

The role of the nucleolus in the control of cell proliferation in mammalian cells is becoming increasingly clear. Our expanding knowledge of the cellular and molecular mechanisms that regulate cell division in normal and cancerous cells opens new possibilities for improving the diagnosis, prognosis, and therapy of tumors.

Nucleolar antigens of normal rat liver, regenerating liver, and Novikoff ascites hepatoma cells were transplanted in vitro from polyadenylic acid-containing messenger RNAs isolated from the respective tissues and immunoprecipitated with specific antinucleolar antibodies and Protein A. By two-dimensional gel electrophoresis of the translation products, five antigens were detected in normal rat liver. The antigens detected in 18-hr regenerating rat liver were the same as those of normal rat liver when immunoprecipitated with the anti-liver nucleolar antibodies. In the Novikoff tumor, 11 antigens were detected with anti-Novikoff nucleolar antibodies. Of these, two were not found in either normal or regenerating liver. Four major antigens were detectable in both Novikoff hepatoma and regenerating liver messenger RNA translation products with anti-Novikoff nucleolar antibodies. Two antigens were found in normal and regenerating liver that were not found in Novikoff hepatoma. In agreement with previous results, these immunoprecipitation analyses provide further evidence that some nucleolar antigens are present in Novikoff hepatoma that are not found in either normal or regenerating rat liver.

The presence of common nucleolar antigens in a broad array of human malignant tumors has led to several lines of investigations. In addition to studies on an increasing number of benign and malignant neoplasms with a variety of antibodies designed to statistically evaluate the presence of nucleolar antigens, purification procedures and chemical analyses are being used to characterize the specific antigens. The localization of the nucleolar antigens in HeLa cells was studied by the postembedding immunoelectron microscopic procedure employing rabbit antibodies to nucleoli or nuclear Tris extracts of these cells. The products of the peroxidase-antiperoxidase complexes visualized by the reaction with diaminobenzidine in nucleoli were mainly found in the nucleolonemas which contain the dense nucleolar RNP components. When these nucleoli became compact after treatment of HeLa cells with adriamycin, the distribution of the immunoreactive products was altered along with distribution of the dense nucleolar components. The human nucleolar antigens were mainly localized to nucleolar regions containing the nucleolar RNP components. Improved purification of the antigens made it possible to provide a satisfactory amino acid analysis of one pI 6.3 antigen. Interestingly, some of the nucleolar antigen was found in miniparticle undescribed until now.

Identification of the immunologic specificity of antinuclear antibodies (ANAs) in the various systemic rheumatic diseases has become increasingly important. The standard immunofluorescence technique may enable detection of antibodies to nuclear antigens present in abundance in the nucleus, such as DNA, histones, Sm, nuclear ribonucleoprotein (nRNP), and SS-B/La. The nuclear antigens present in low concentrations, such as SS-A, proliferating cell nuclear antigen (PCNA), rheumatoid arthritis nuclear antigen (RANA), and Ku antigens, are unique to cell types, and their detection requires special substrates or reagent systems. Anti-Sm, anti-Scl-70, anticentromere, and anti-PM-1 are characteristic serologic markers for systemic lupus erythematosus, scleroderma, the CREST syndrome of scleroderma, and polymyositis, respectively. Distinct profiles of ANA characterize different rheumatic diseases. A number of ANAs are found in SLE, whereas other diseases are characterized by the presence or absence of a certain ANA or by differences in mean ANA titers. Specific ANAs have been used to isolate and characterize nuclear antigens at molecular and functional levels.

We identified, by anticomplement immunofluorescence, a nuclear antigen (hepatitis B virus-associated nuclear antigen [HBNA]) in two human hepatoma cell lines containing integrated hepatitis B virus DNA but not in three hepatoma cell lines lacking it. The antigen resembled neoantigens associated with the oncogenesis of certain papovaviruses, adenoviruses, and herpesviruses. Antibody to the antigen (anti-HBNA) was found in 7.3% of hepatitis B surface antigen-positive sera from patients with hepatocellular carcinoma but not in surface antigen-negative sera. The staining of HBNA was characterized by two patterns, reticular nuclear fluorescence and nucleolar fluorescence. The expression of HBNA did not parallel the production of extracellular hepatitis B surface antigen. Treatment of cells with proteinase K, RNase, DNase, or cycloheximide significantly diminished the staining of HBNA.

Molecular analysis of the proliferating cell nuclear antigen (PCNA) has the 2-fold goal of utilizing the unique tools provided by autoimmune sera to study the function of this important intracellular molecule and to provide insights into the etiology of autoimmune disease. PCNA is expressed in the nucleus immediately preceding S phase and, during S phase is colocalized with sites of active DNA synthesis. There is currently available not only a battery of human sera which can be rendered monospecific for PCNA, but also monoclonal antibodies and rabbit antipeptide antibodies. With these reagents, it might be possible to isolate cDNA clones from cDNA expression libraries.

During the primary immune response induced by the administration of sheep erythrocytes in mice, nucleolar activation was observed in macrophages, lymphocytes as well as in plasmacytes. The first maximum (4.6%) was observed on day 3 in macrophagic cells. Maximal activation of plasmoblasts (6.6%) and plasmacytes (5.9%) was observed on day the lymphoid series the first maximum in the occurrence of cells showing specific immunological activatin was as follows: large lymphocytes on day (6.5%), medium-sized lymphocytes on day 7 (6.6%) and, ultimately, small lymphocytes (6.3%) on day 8. The study verified the possibility of using nucleolar staining for estimating its functional morphology and thus following the changes of specific immunological activation during the primary immunological response.

In an extension of previous studies on the antigens in rat liver nucleoli (R. K. Busch, R. C. Reddy, D. H. Henning, and H. Busch, Proc. Soc. Exp. Biol. Med. 160, 185 (1979); R. K. Busch and H. Busch, Tumori 63, 347 (1977); F. M. Davis, R. K. Busch, L. C. Yeoman, and H. Busch, Cancer Res. 38, 1906 (1978), rabbit antibodies were elicited to human liver nucleoli isolated by the sucrose--Mg2+ method (10). Fluorescent nucleoli were found in liver cryostat sections treated with rabbit anti-human liver nucleolar antibodies followed by fluorescein-conjugated goat anti-rabbit antibodies. In HeLa cells, fluorescence was distributed throughout the nucleus and in a nuclear network but was not localized to the nucleolus. In placental cryostat sections, an overall nuclear fluorescence was observed with some localization to nucleoli. Immunodiffusion analysis revealed two immunoprecipitin bands which appeared to be liver specific. Other immunoprecipitin bands were common to liver, placenta, and HeLa nuclear extracts. Rocket immunoelectrophoresis revealed two liver-specific antigens, one migrating to the cathode and the other to the anode Other rockets exhibited identity to antigens of other nuclear extracts. These results demonstrate the presence of human liver nucleolar-specific antigens which were not found in the HeLa and placental cells.

A new method is described for determining the distribution of epitopes identified by monoclonal antibodies. The method utilizes nitrocellulose membranes as a solid support for antigens which are rapidly adsorbed to nitrocellulose by vacuum-blotting and then used in competitive antibody binding assays. The distribution of epitopes is established by the reciprocal cross-blocking of radiolabeled antibody by increasing concentrations of unlabeled antibody. When unlabeled antibody does not block the binding of labeled antibody to antigen, the 2 antibodies recognize distinct epitopes. When unlabeled antibody blocks the binding of labeled antibody to antigen, the 2 antibodies recognize the same epitope. The method is rapid, sensitive and should be applicable to screening monoclonal antibodies to any epitope.

In interphase cells the proliferation-associated antigen recognized by monoclonal antibody Ki-67 is almost exclusively located in the nucleoli. When cells at several stages of mitosis were examined for the localization of the Ki-67 antigen, a striking redistribution could be observed. During prophase the distinct nucleolar Ki-67 fluorescence changed to a bright irregular meshwork throughout the nucleoplasm. At metaphase the antigen appeared to be distributed in a reticulate structure surrounding the condensed chromosomes, while at late telophase a punctated staining of the entire nucleoplasm was observed, which preceded the typical nucleolar localization pattern in each of the two daughter cells. Immunolabelling with Ki-67 of metaphase chromosome spreads revealed a circumferential staining of the individual chromosomes. The Ki-67 antigen is preserved in nuclear matrix preparations obtained after in situ fractionation of interphase cells. When mitotic cells were exposed to such treatments, the obtained fluorescence data suggested that the antigen may be part of the chromosome scaffold. Quantification of the Ki-67 fluorescence signal using flow cytometry revealed the highest staining intensities in mitotic cells. Furthermore, it was shown that nutritionally deprived cells became negative for Ki-67.

Tumor burden in adult patients with acute leukemia is assessed using the percentage of blast cells in the bone marrow or blood. It is clear, however, that not all blast cells are leukemic cells, especially during rapid marrow regeneration. Similarly, some leukemia cell lines have been shown to differentiate in vitro, and the same process also occurs in vivo. Therefore, the leukemic burden may be due to more differentiated cells as well as to blast cells. The purpose of this study was to investigate whether the human malignancy-associated nucleolar antigen (HMNA) could be used as a marker for leukemic cells and to examine its potential as a diagnostic tool. The proportion of HMNA-positive cells in the bone marrow of patients with acute leukemia was determined by indirect immunofluorescence with antibodies to HMNA and was compared with the differential counts routinely made in the clinic laboratory. The percentages of HMNA-positive cells among the nucleated cells in the marrow of 72 patients with clinical evidence of leukemia were significantly higher (range 9%-98%, median 83%) than those observed for nonleukemic individuals (range less than 0.05%-2.5%, median 1%) or for fractions of marrow cells from normal volunteers enriched for normal early progenitor cells (less than or equal to 2%). Patients with leukemia in remission had a lower percentage of HMNA-positive cells (range 0%-83%, median 3%). The percentage of HMNA-positive cells increased as patients approached relapse. Although the percentage of HMNA-positive cells was related to the percentage of blast cells in the bone marrow of the patients with leukemia, some partially differentiated cells were also HMNA-positive in some specimens, and some blastic cells were HMNA-negative in other specimens. These studies indicate the potential usefulness of HMNA as a marker for leukemic cells.

Previous studies of Xenopus laevis embryos homozygous for the nucleolar deletion mutation have concluded that these embryos contain few, if any, copies of the genes for the 18 S and 28 S ribosomal RNAs. Using hybridization to restriction endonuclease digests of DNA it is found, in fact, that a small amount of ribosomal DNA is still present in such embryos. The ribosomal DNA in these embryos appears to include a few normal repeats together with a variety of unusual fragments containing either spacer or gene sequences. An antibody found in the serum of a scleroderma patient reacts with an antigen localized in the nucleoli of wild-type embryos. In anucleolate embryos this antigen is found in the so-called pseudonucleoli and in many small bodies in the nuclei.

Nucleolar chromatin of Novikoff hepatoma ascites cells contains an antigen (no-Ag1) detected with antinucleolar antibodies by the immunodiffusion technique. This antigen was distinguished from the previously reported nuclear chromatin antigen NAg-1 (19) by the findings that tumor nucleolar antibodies which formed immunoprecipitin bands with no-Ag1 did not do so with NAg-1 and that tumor cytosol, which contains NAg-1, formed immunoprecipitin bands with tumor chromatin antibodies but not with antibodies to tumor nucleoli. Tumor nucleolar chromatin contains both NAg-1 and no-Ag1, but only no-Ag1 formed bands with tumor nucleolar antibodies, no-Ag1 is a component of tumor nucleolar chromatin that was not soluble in 0.075 M NaCl-0.025 M EDTA, pH 8, and only slightly soluble in 0.01 M Tris-HCl, pH 8. NO-Ag1 was not found in liver nucleoli. Antibodies to liver nucleoli formed immunoprecipitin bands with liver nucleolar antigens but none were confluent with those formed between tumor nucleolar antibodies and antigens of tumor nucleolar chromatin. Absorption of the tumor nucleolar antibodies with whole tumor cells or whole liver pressate did not alter band formation with no-Ag1. Three antigens in liver nucleoli were not found in tumor nucleoli.

Epidermal nucleolar IgG deposition in clinically normal skin reflects high serum concentrations of antibody to nucleolar antigen. This immunopathologic finding occurred in six patients with scleroderma and in two patients with a scleroderma-systemic lupus erythermatosus overlap syndrome.

Forty-one patients with various forms of systemic sclerosis (scleroderma) and positive antinuclear antibodies of nucleolar (ten patients), speckled (eleven patients), or centromere pattern (twenty patients) were selected for study of immune complexes by the radioisotope labeled Clq binding and the radioisotope labeled protein A binding methods. The presence of immune complexes was found by the Clq binding assay in sixteen patients (39%) and by a protein A binding assay in eight patients (20%). Overall, 46% of patients (19/41) had immune complexes. A lower incidence of organ involvement and fewer positive results in the screening of serum immune complexes were observed in patients with centromere antibody (35%) than in patients with nucleolar (60%) or speckled pattern (55%). Patients with immune complexes had higher frequencies of kidney, heart, and muscle involvement and digital ulceration than did patients with no detectable immune complexes, but the differences were not statistically significant. Diffuse skin involvement was not related to the presence of immune complexes.

In scleroderma a profusion of circulating autoantibodies have now been defined. They include autoantibodies to Scl-70 or DNA topoisomerase 1, and to centromere/kinetochore proteins of 17.80 and 140 kilodaltons. In addition, there are several antigens which are resident primarily in the nucleolus and they are RNA polymerase 1, PM-Scl, fibrillarin and 7-2 ribonucleoprotein. Antibody to Scl-70 has been found primarily in the diffuse form of scleroderma and antibody to the centromere/kinetochore proteins in the CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia) subset of scleroderma. Autoantibodies to the nucleolar antigens RNA polymerase 1, PM-Scl, fibrillarin and 7-2 RNP have been detected in at least 10% of all patients with scleroderma. For several reasons which are discussed, it appears that the autoantibody response in scleroderma is antigen-driven and further that the autoantigens involved in this disease are present at some time in the nucleolus. These observations may be providing clues to some of the basic mechanisms initiating autoimmunity.

With rabbit antibodies to nuclear 0.01 M Tris-HCl, pH 8, extract or "nucleolar preparations" of human HeLa S3 cells and fluorescein-labeled goat anti-rabbit antibodies, bright nucleolar immunofluorescence was observed in 61 or 63 human adenocarcinomas, squamous cell carcinomas, sarcomas, hematological neoplasms, and other malignant tumors. With these antibodies, nucleolar immunofluorescence was not found in 23 normal tissue specimens, 10 benign adenomas and hyperplastic tissues, and 8 specimens of inflammatory diseases. In the nontumorous tissues examined, positive nucelolar fluorescence was found in a few sections of a gastric ulcer and chronic ulcerative colitis which have been known propensities for malignant change; these areas may have been undergoing focal malignant changes.

To compare regulation of nucleolar function of tumors and other tissues, it was necessary to develop assays of the fidelity of ribosomal DNA readouts. For this purpose, homochromatography analyses of complete T1 ribonuclease digestion products of the in vivo labeled 45 S preribosomal RNA were compared with those of 18S and of 28 S ribosomal RNA. Homochromatography analysis of the in vitro readout product of isolated nucleoli showed the presence of many large marker nucleotides of the in vivo 45 S preribosomal RNA. Moreover, no other large oligonucleotides were detected. The in vitro readout product of nucleolar chromatin had the same T1 ribonuclease digestion products, including the large marker of oligonucleotides. However, the in vitro readout product of nucleolar DNA contained no large marker T1 ribonuclease oligonucleotides. These results indicate that the fidelity of nucleolar readouts is controlled by regulatory proteins of the nucleolar chromatin. Differences were found in nucleolar proteins of normal rat liver and Novikoff hepatoma by immunological analyses. The possibility exists that differences in readout rates of tumor and other nucleoli are related to the protein difference detected by these immunological studies.