anti-H1 Antibodies Research Articles

Multiple Sclerosis: Enzymatic Cross Site-Specific Hydrolysis of H1 Histone by IgGs against H1, H2A, H2B, H3, H4 Histones, and Myelin Basic Protein.

Histones play a key role in chromatin remodeling and gene transcription. Further, free histones in the blood act as damage-associated molecules. Administration of histones to animals results in systemic inflammatory and toxic effects. Myelin basic protein is the principal constituent element of the myelin-proteolipid sheath of axons. Abzymes (antibodies with catalytic activities) are the original features of some autoimmune diseases. In this study, electrophoretically homogeneous IgGs against H1, H2A, H2B, H3, and H4 histones and myelin basic protein (MBP) were isolated from the blood sera of multiple sclerosis (MS) patients by several affinity chromatographies. Using MALDI mass spectrometry, the sites of H1 histone cleavage by IgGs against H1, H2A, H2B, H3, H4, and MBP were determined. It was shown that IgGs against H1 split H1 at 12 sites, while the number of cleavage sites by abzymes against other histones was lower: H2A (9), H2B (7), H3 (3), and H4 (3). The minimum rate of H1 hydrolysis was observed for antibodies against H3 and H4. A high rate of hydrolysis and the maximum number of H1 hydrolysis sites (17) were found for antibodies against MBP. Only a few sites of H1 hydrolysis by anti-H1 antibodies coincided with those for IgGs against H2A, H2B, H3, H4, and MBP. Thus, the polyreactivity of complexation and the enzymatic cross-activity of antibodies against H1, four other histones, and MBP have first been shown. Since histones act as damage molecules, abzymes against histones and MBP can play a negative role in the pathogenesis of MS and probably other different diseases as well.

Pandemic influenza virus vaccines boost hemagglutinin stalk-specific antibody responses in primed adult and pediatric cohorts

Licensed influenza virus vaccines target the head domain of the hemagglutinin (HA) glycoprotein which undergoes constant antigenic drift. The highly conserved HA stalk domain is an attractive target to increase immunologic breadth required for universal influenza virus vaccines. We tested the hypothesis that immunization with a pandemic influenza virus vaccine boosts pre-existing anti-stalk antibodies. We used chimeric cH6/1, full length H2 and H18 HA antigens in an ELISA to measure anti-stalk antibodies in recipients participating in clinical trials of A/H1N1, A/H5N1 and A/H9N2 vaccines. The vaccines induced high titers of anti-H1 stalk antibodies in adults and children, with higher titers elicited by AS03-adjuvanted vaccines. We also observed cross-reactivity to H2 and H18 HAs. The A/H9N2 vaccine elicited plasmablast and memory B-cell responses. Post-vaccination serum from vaccinees protected mice against lethal challenge with cH6/1N5 and cH5/3N4 viruses. These findings support the concept of a chimeric HA stalk-based universal influenza virus vaccine. clinicaltrials.gov: NCT02415842.

Autoantibodies in HIV-infected patients: Cross site-specific hydrolysis of H1 histone and myelin basic protein.

Histones act as damage-associated molecules, while anti-DNA antibodies are directed against histone-DNA nucleosomal complexes. Myelin basic protein (MBP) plays an important role in the pathogenesis of multiple sclerosis. Autoantibodies (Abs) with enzymatic activities are the distinctive feature of some autoimmune and viral diseases. Abzymes with proteolytic activity against different proteins specifically hydrolyze only these specific proteins. Using chromatography of IgGs on columns with immobilized H1 histone and then by chromatography of the fraction having an affinity for the histone (eluted upon loading) on MBP Sepharose, the anti-MBP antibodies were obtained. Anti-H1 antibodies were obtained using these columns in reverse order. IgGs against H1 and MBP effectively hydrolyze both H1 histone and MBP but no other control proteins. Using the MALDI mass spectrometry, the cleavage sites of H1 histone and MBP by abzymes against these proteins are found. The hydrolysis of MBP by anti-MBP IgGs occurs at four clusters (22 sites of the hydrolysis) locating at four known antigenic determinants of MBP. Anti-H1 Abs hydrolyze MBP only at one cluster (11 sites of the hydrolysis); this cluster is only partially overlapped with one of the four MBP clusters. Anti-H1 antibodies hydrolyze H1 at five sites of one cluster of the protein when anti-MBP IgGs cleavage this histone at two clusters containing 17 sites of the cleavage. Anti-H1 and anti-MBP abzymes are the first examples of Abs possessing not only with cross-complexing but also with catalytic cross-reactivity. The existence of cross-reactivity of abzymes against histones and MBP represent great danger to humans. © 2018 BioFactors, 45(2):211-222, 2019.

Assessment of the influenza vaccine (VAXIGRIP) in triggering a humoural immune response.

ObjectivesThe World Health Organization (WHO) has announced a pandemic alert following successive waves of H1N1 epidemics that have swept the world. KSA became vulnerable to influenza virus due to Hajj and Umrah pilgrimages. Antibodies have been tested to inhibit the attachment and spread of influenza viruses to epithelial cells. This study aimed to assess the immunological indices of the influenza vaccine, VAXIGRIP, in triggering humoural immunity in volunteers.MethodsSera from pre- and 14 days post-vaccinated subjects were analysed for haemagglutinin (HA)-specific anti-H1 and anti-H3 antibodies using ELISA. Expansion of CD19+ B cells was quantified using FACSCalibur.ResultsThe VAXIGRIP vaccine induced specific anti-H1 and anti-H3 HA IgG antibodies against H1N1 and H3N2 influenza viruses, respectively. There was a significant increase in B cell numbers post-vaccination that directly matched the anti-H1 antibody titre. The results suggest that B cells are likely to be primed by the same antigenic strain derived from both H1N1 and H3N2 viruses, which were likely to be included in the vaccine.ConclusionInfluenza vaccine triggered a humoural immune response to surface HA proteins in vaccinated subjects. To our knowledge, this is the first report corroborating the immunogenicity of the influenza vaccine in KSA volunteers. These results may be beneficial to the ministry of health and the Saudi FDA in terms of weighing the role of this vaccine in inducing protective immunity.

Development and characterization of neutralizing monoclonal antibodies against the pandemic H1N1 virus (2009)

The 2009 H1N1 influenza pandemic was a major international public health crisis which caused considerable morbidity and mortality worldwide. The goal of this study was to produce anti-H1 monoclonal antibodies (MAbs) for improving diagnostic immunological assays and to develop potential immunotherapeutics. Nine MAbs were produced after immunizing mice with recombinant hemagglutinin (HA) protein from A/California/06/09. Two spleenocyte myeloma fusions yielded 1588 hybridoma cultures. After screening the hybridoma culture supernatants for antibody reactivity to rHA, nine clones were selected for further characterization. Cross-reactivity studies of the anti-rHA antibodies against a panel of influenza viruses (H1-H16) revealed eight out of nine MAbs were specific to the pandemic H1 subtype, except for MAb F256G2sc1 which also cross-reacted with H5 subtype virus. All MAbs were of the IgG1κ isotype, except F256G2sc1 which was IgG2aκ. The anti-rHA MAbs had binding affinities to rHA that ranged from a K(D) (disassociation constant) of 1.34×10(-9)M (F255G7sc1) to the weakest affinity of 4.60×10(-8)M (F255G4sc1). Interestingly, in a plaque reduction neutralization assay, all MAbs except F255G3sc1 demonstrated neutralizing ability. Furthermore, all MAbs except F255G3sc1 and F255G9sc1 exhibited anti-hemagglutinin activity against pandemic H1N1 viruses, but not against classical North American swine influenza viruses of the same subtype. Immunofluorescence assay (IFA) demonstrated that all MAbs except F255G1sc1 and F255G3sc1 were able to detect 2009 pandemic H1N1 (2009) virus- infected MDCK cells. The MAbs were also evaluated for potential use in competitive ELISA (cELISA), and with the exception of F255G3sc1, all MAbs showed competitive activity with serum collected from pigs infected with pandemic H1N1 virus (2009). The developed MAbs have demonstrated utility as immunodiagnostic and research reagents, and their neutralizing capabilities also hold potential for designing antiviral drugs against pandemic influenza.

Serologic Evidence of Pandemic (H1N1) 2009 Infection in Dogs, Italy

Serologic Evidence of Pandemic (H1N1) 2009 Infection in Dogs, Italy

Inhibition of histone/anti-histone reactivity by histone-binding serum components; differential effect on anti-H1 versus anti-H2B antibodies.

IgG fractions were purified on a protein G-agarose column from sera of both systemic lupus erythematosus (SLE) patients and healthy donors. All IgG fractions, after elution with 0.5 M acetic acid, reacted with histones in an anti-histone ELISA assay, and IgG anti-histone activity was in all instances higher in the IgG fraction than in the corresponding whole serum. This was shown to be due to the presence in serum of histone-binding components that inhibited IgG binding to histones. Both normal human and SLE patients' sera had these histone-binding components, and disparity between serum-positive and -negative anti-histone antibody (AHA) tests was not dependent on differences in the blocking capacity but on IgG antibody levels and avidity. Interaction of normal serum IgG fraction with all five histones was of low avidity, whereas interaction of IgG from AHA-positive SLE sera with both H1 and H2B had high avidity. Low-affinity antibodies to every histone fraction, but also high-affinity anti-H1 antibodies, were preferentially inhibited. Our data indicate that several serum protein components are inhibiting histone/anti-histone interaction and may play a protective role against both high-affinity anti-H1 antibodies present in SLE patients, and natural, low-affinity, anti-histone antibodies. As some acute phase proteins, notably C-reactive protein, bind to histones, it is conceivable that they play such a role. High-affinity anti-H2B antibodies, present in some SLE patients, and not inhibited by these serum components, may, on the other hand, participate in the pathogenesis of the disease.

Specificities of IgM and IgG anti-histone H1 autoantibodies in autoimmune mice

Autoantibodies to histone H1 represent the most common specificity among anti-histone autoantibodies in systemic autoimmune diseases. Here we analyse anti-H1 autoantibodies in mice from the following autoimmune strains: MRL/Mp-lpr/lpr, NZB and NZB x NZW/F1. Autoantibodies of the IgM isotype bind predominantly to epitopes located in the COOH-terminal domain of the H1 molecule, whereas IgG autoantibodies in the MRL/Mp-lpr/lpr and NZB strains also recognize epitopes requiring the integrity of both the COOH-terminal and the central globular domains of H1. In both of these strains, the titre of these IgG anti-H1 antibodies rises during the course of the disease. The importance of three-dimensional structure of histone H1 was attested by a significant decrease in IgG binding after cleavage of the H1 molecule within the folded globular domain. The binding of these sera to H1 variants from various species was also investigated and a strong binding of MRL/Mp-lpr/lpr sera to certain phylogenetically distant histone H1 variant molecules (sea-urchin sperm H1 and chicken erythrocyte H5) was observed. This cross-reacting binding can be explained by the presence in MRL/Mp-lpr/lpr sera of autoantibodies to H1(0), a variant found in non-dividing cells and exhibiting sequence homologies to the above mentioned variants. The significance and the possible implications of these data for the pathogenesis of autoimmunity are discussed.

Anti-histones antibodies in systemic lupus erythematosus: prevalence and frequency in neuropsychiatric lupus.

To investigate the specificity, sensitivity, and concomitant presence of antibodies against histones (H), histone H1 (H1), and histone H3 (H3) in patients with systemic lupus erythematosus (SLE) and analyze their association with SLE. Serum IgG anti-histones antibodies were detected by enzyme-linked immunosorbent assay in 144 SLE patients consisting of 24 neuropsychiatric lupus (NPSLE), 65 lupus nephritis (LN), and 55 SLE, 100 other rheumatic diseases patients, as well as 40 healthy controls. Clinical and biological parameters of the patients were also evaluated. Anti-H, anti-H1, and anti-H3 antibodies yielded a sensitivity of approximately 33% and a specificity of more than 93% for SLE, which was comparable to that found for anti-double-stranded DNA (anti-dsDNa) antibodies. More significantly, anti-histone antibody is found in approximately 50% of patients with NPSLE compared with LN. Moreover, the titers of anti-histones antibodies of NPSLE patients were significantly higher than that of patients with SLE and LN. The sequential analysis revealed a close correlation of anti-H and anti-H1 antibodies with SLE disease activity. There was an approximate 30% positive rate of anti-histones antibodies in 144 SLE patients lacking anti-nucleosome, anti-mDNA, anti-Sm, and anti-dsDNA antibodies. Antibodies to histones H1 and H3 are markers with high specificity of 93.6-96.4% for SLE. The anti-histone antibody markers are prevalent in approximately 50% of NPSLE. Furthermore, there was a strong correlation with SLE disease activity index and levels of antibodies to histones and H1.

The autoimmune response to chromatin antigens in systemic lupus erythematosus: autoantibodies against histone H1 are a highly specific marker for SLE associated with increased disease activity.

This study investigates specificity, sensitivity and concomitant presence of antibodies against histone H1 (H1), nucleosomes (NUC), chromatin (CHR) and dsDNA in patients with systemic lupus erythematosus (SLE), analyses their association with SLE disease activity and characterizes the immunodominant epitope reactivity of anti-H1 antibodies and its relation to SLE disease activity. In a cross-sectional study 394 sera of patients with various rheumatic diseases and healthy subjects were analysed by ELISA for antibodies against H1, NUC, CHR and dsDNA. In addition, a longitudinal analysis was performed that included 121 sequential serum samples derived from 16 SLE patients to assess the relation of these antibodies as well as antibodies to histone H2B to SLE disease activity. To assess epitope reactivity of anti-H1 antibodies overlapping synthetic peptides covering the entire H1 sequence were used. Anti-H1 antibodies yielded a sensitivity of approximately 45% and a specificity of over 98% for SLE, which was comparable to that found for anti-dsDNA antibodies. Anti-CHR and anti-NUC antibodies were of similar sensitivity but slightly (anti-CHR) or considerably (anti-NUC) less specific for SLE (95 and 85%, respectively). The sequential analysis revealed a strong correlation of anti-H1 antibodies with SLE disease activity that was better than the correlation of anti-dsDNA and anti-NUC antibodies, while only weak correlation was found for anti-CHR and anti-H2B antibodies. The immunodominant epitope for anti-HI was localised between amino acids 204 and 218 (pp204-218) and immune reactivity to this epitope also correlated with disease activity. Anti-H1 is a highly specific marker for SLE with a diagnostic value comparable to anti-dsDNA. A positive testing for anti-H1 indicates increased disease activity, as does the appearance of antibodies to its immunodominant epitope pp204-218.

A Novel Assay to Demonstrate an Intersection of the Exocytic and Endocytic Pathways at Early Endosomes

The mechanism of transport of membrane proteins from the trans-Golgi to the cell surface is still poorly understood. Previous studies suggested that basolateral membrane proteins, such as the transferrin receptor and the asialoglycoprotein receptor H1, take an indirect route to the plasma membrane via an intracellular, most likely endosomal intermediate. To define this compartment we developed a biochemical assay based on the very definition of endosomes. The assay is based on internalizing anti-H1 antibodies via the endocytic cycle of the receptor itself. Internalized antibody formed immune complexes with newly synthesized H1, which had been pulse-labeled with [35S]sulfate and chased out of the trans-Golgi for a period of time that was insufficient for H1 to reach the surface. Hence, antibody capture occurred intracellularly. Double-immunofluorescence labeling demonstrated that antibody-containing compartments also contained transferrin and thus corresponded to early and recycling endosomes. The results therefore demonstrate an intracellular intersection of the exocytic and endocytic pathways with implications for basolateral sorting.

134 REACTIVITY TO NATIVE ASIALOGLYCOPROTEIN RECEPTOR AND ITS SUBUNITS IN AUTOIMMUNE LIVER DISEASE

Asialoglycoprotein receptor (ASGPR) is a component of the hepatocyte membrane and the suggested target of tissue-damaging immune responses in autoimmune liver disease, nearly 90% of patients with autoimmune hepatitis having circulating autoantibodies against this receptor at titres that correlate closely with the histological severity of the disease. Native human ASGPR is a dimer or a trimer composed of two subunits: H1 of 46 kD and H2 of 50 kD with 60% homology. We have introduced the cDNAs of human ASGPR H1 and H2 subunits individually into NIH 3T3, a murine fibroblast cell line. Using a technique of indirect immunofluorescence, anti-native ASGPR antibodies demonstrated membrane expression of either subunit by UV-microscopy and cytofluorimetry. Immunoblot analysis also showed presence of the proteins in the cytoplasm of the transfected cells. We also assessed whether sera from patients with autoimmune liver disease react with the individually expressed ASGPR subunits and to what extent this reactivity is related to that against native ASGPR. Reactivity to H1 and H2 was investigated by indirect immunofluorescence and compared to that against native ASGPR assessed by radioimmunoassay (RIA). Sera from 20 patients, age range 4-20 yrs (median 12 yrs), with autoimmune liver disease (14 autoimmune hepatitis, 6 autoimmune sclerosing cholangitis) and 9 age matched healthy controls were tested. Anti-native ASGPR antibodies were detected in 11 patients (titre 1/200 - 1/2000 by RIA). Of these 11 sera, 2 were positive for anti-H1 antibodies alone, 3 were positive for both anti-H1 and anti-H2, and 6 showed no reaction. Of the 9 sera unreactive to native ASGPR, none reacted with the individual subunits. None of the 9 control sera reacted with H1 or H2 subunits or with the native ASGPR. The reactivity to native ASGPR was significantly correlated to that against subunits (p < 0.05). Our findings demonstrate that some epitopes target of autoimmunity are conserved when ASGPR is expressed in a monomeric form while others are present only on the full receptor.

Effects of H1 histones and a monoclonal autoantibody to H1 histones on clot formation In vitro: Possible implications in the antiphospholipid syndrome

Histones are known to bind anionic phospholipids (PLs). Binding of procoagulant PLs by histones released during cell injury/death may interfere with coagulation and may serve a local regulatory anticoagulant function. Histone H1 prolonged the PT and APTT of normal pooled plasma (NPP). These increased clotting times disappeared when anti-H1 monoclonal antibody (mAb) was added to the incubation. Dilute Russell Viper Venom Time was also prolonged with the addition of histone H1. When H1 was added to plasma from a patient with the antiphospholipid syndrome (APL plasma), there was a further prolongation of the abnormal APL clotting time which was partially corrected by anti-H1 mAb. Platelet neutralization times were increased with added H1 and were further increased using APL plasma. When disrupted endothelial cells were incubated with plasma with and without anti-H1 antibodies, the addition of anti-H1 antibodies decreased clotting times. These data support the theory that histones released during cell injury may have a regulatory anticoagulant role in clot formation and the anti-H1 effect of some APL plasmas may inhibit this, thereby contributing to thrombosis seen in APL patients.

Antibodies specific to histone H1 inhibit in vitro transcription in isolated mammalian nuclei.

The issue of whether histone H1 is present in transcriptionally active chromatin has been approached by studying the effect specific anti-H1 antibodies have on in vitro transcription in isolated nuclei. To that end, the incorporation of radioactive RNA precursors into trichloroacetic acid-precipitable material was compared for control nuclei and nuclei that had been preincubated with specific anti-H1 antibody populations (whole sera, affinity-purified immunoglobulins and monovalent Fab fragments). The anti-H1 antibodies significantly and reproducibly inhibited the transcriptional activity in isolated nuclei. Experiments were also performed to exclude the possibility that the inhibition observed was due to some long-distance effect of the binding of the antibodies to chromatin. The results are interpreted as indicating that active gene chromatin does contain histone H1.

Epitope recognition in histone H1 by SLE autoantibodies in the presence of a DNA-ligand.

To investigate the specificity of anti H1 antibodies peptides from the N- and C-domain of H1 and the synthetic oligonucleotide (AT)6 were complexed. Circular dichroism (CD) spectroscopy indicated that the free peptides H1(1-16), H1(204-218) and C(121-210) in low salt buffer assume a random structure but become helical when bound to the oligonucleotide. The structured and unstructured H1 fragments were then analyzed by enzyme linked immunosorbent assay (ELISA) with anti-H1 antibodies in sera from patients with systemic lupus erythematosis (SLE) and with the monoclonal anti-H1 antibody MRA-12 derived from MLR lpr/lpr autoimmune mice. Binding of these antibodies to H1(204-218) and C was inhibited to a level of 50% when these H1 peptides were complexed with (AT)6. When the same antibody was tested with H1 fragment GC(34-210), attachment to oligonucleotide (AT)6 did not influence antibody binding. Competition studies with liquid phase GC and C antigen against solid phase GC and C indicated that liquid phase GC was more efficient in displacing antibody binding reactivity than liquid phase C. The displacement effect of both liquid phase antigens was greatest against solid phase C. We conclude that anti-H1 autoantibodies are directed against an epitope located near the junction of the G- and C-domain which is exposed and not masked when H1 is bound to DNA.

The Role of CD45RA on Human B‐Cell Function: Anti‐CD45RA Antibody (Anti‐2H4) Inhibits the Activation of Resting B Cells and Antibody Production of Activated B Cells Independently in Humans

Anti-CD45RA antibody defined by anti-2H4 monoclonal antibody has been reported to split CD4+T cells into two distinct subpopulations. CD45RA antigen is present on the surface of virtually more than 95% B lymphocytes in the purified tonsillar B-cell preparations. We examined the role of CD45RA antigen on human B-cell function using this antibody. The addition to anti-2H4 to tonsillar B cells inhibited the proliferative response induced by Staphylococcus aureus Cowan strain I(SAC) in a dose-dependent manner. Kinetic analysis indicated that anti-2H4 exerted its inhibitory effect when added within the first 24 h of culture initiation during a 72-h culture period. Anti-2H4 inhibited the transferrin receptor expression without interfering with the expression of the IL-2 receptor on SAC-stimulated B cells in a short-term culture. Anti-2H4 blocked the progress of SAC-stimulated B cells from the G1 to S phase of the cell cycle. These events suggested that anti-CD45RA MoAb inhibited the proliferative response by directly acting on B cells in the G1 phase. In addition, anti-CD45RA antibody also had a suppressive effect on early phase of B-cell differentiation. This effect appeared to be independent of its suppressive effect on proliferation, because anti-CD45RA did not inhibit the proliferative response of preactivated B cells with lymphokines. These studies suggested that the restricted epitope recognized by anti-2H4 antibody may be directly involved in regulatory function on B cells.

Anti-histone antibodies in subacute sensory neuropathy.

We investigated the levels of anti-histone antibodies in the sera of 7 patients with subacute sensory neuropathy. IgG antibodies to histones H1 and H3 were significantly elevated in 4 of these patients. The anti-H1 antibodies reacted mainly with determinants located in the central globular and the carboxy-terminal domain of the H1 molecule. We also observed reactivity of these sera with histone H1 zero, a variant found in terminally-differentiated cells such as neurons. This study suggests a potential for histones to serve as autoantigens in humorally-mediated paraneoplastic diseases.

Antihistone antibodies in antinuclear antibody—positive juvenile Arthritis

The binding of antinuclear antibody-positive juvenile arthritis (JA) sera to bovine thymus histones H1, H2A, H2B, H3, and H4 was studied by an enzyme-linked immunosorbent assay. Seventy-five percent of the JA patients tested positive for at least 1 antibody specificity. Antihistone antibodies were predominantly IgM, while IgG antibodies were less common and were restricted to histones H1 or H3. In the group of patients with JA of pauciarticular onset, antihistone antibodies were significantly more elevated in patients with past or present uveitis than in patients without a history of uveitis. Anti-H1 antibodies in JA patients were found to react mostly with determinants located in the carboxyl-terminal domain of the H1 molecule. Sera were also reactive with human histone H1(0) or chicken histone H5, which are H1 variants found only in nondividing cells.

Chromatin structure of transcriptionally competent and repressed genes.

We have compared transcriptionally competent and repressed genes with respect to their linker histone content and their ability to fold into higher-order structures. Histones were cross-linked covalently to DNA in chicken erythrocyte and oviduct nuclei by UV irradiation, and the DNA that was immunoprecipitated with anti-H1 and (for erythrocytes) anti-H5 antibodies was analysed for particular DNA sequences. None of the sequences investigated was free of H1 (H5). However, in mature erythrocytes the tissue-specific adult beta-globin gene (beta A) appears to be partially depleted of H5, and both the beta-globin gene and the H5 gene (also tissue-specific), as well as the 'housekeeping' beta-actin gene, appear to be partially depleted of H1 relative to inactive genes; in oviduct slight H1-depletion is detected on the ovalbumin gene relative to genes that are inactive in this tissue and the actin gene. Transcriptionally competent erythrocyte chromatin fragments, in contrast to inactive fragments, are unable to self-associate into 'pseudo-higher-order structures'. This is likely to be a consequence of the partial depletion of H5 and/or H1 in active chromatin, resulting in the breakdown of (probably cooperative) interactions between H5 and/or H1 molecules that otherwise mediate the assembly of pseudo-higher-order structures in vitro and a stable 30 nm chromatin filament in vivo.

Autoantibodies against different histone hi subtypes in systemic lupus erythematosus sera

The H1 histones represent the most heterogenous class of histone proteins. In this study, we analyzed the specificity of human antibodies against 6 H1 subtypes. H1 histones from rat organs were separated by reverse-phase high performance liquid chromatography and used as antigens in immunoblotting experiments. Sera containing anti-histone H1 antibodies were obtained from patients with systemic lupus erythematosus. Of the 9 sera tested, 2 reacted with only 1 H1 subtype. The other sera recognized different combinations of H1 subtypes. Only 1 serum reacted with all 6 H1 subtypes. Histones H1.5 and H1.1 were the subtypes most frequently recognized by the human autoantibodies. Our data indicate that human anti-H1 antibodies represent a heterogenous population, directed mainly against epitopes localized in the variable region of the H1 molecule.