Antiplatelet antibody‐induced thrombocytopenia does not correlate with megakaryocyte abnormalities in murine immune thrombocytopenia

Immune thrombocytopenia (ITP ) is an autoimmune bleeding disorder characterized by increased peripheral immune platelet destruction and megakaryocyte defects in the bone marrow. Although ITP was originally thought to be primarily due to antibody‐mediated autoimmunity, it is now clear that T cells also play a significant role in the disease. However, the exact interplay between platelet destruction, megakaryocyte dysfunction and the elements of both humoral and cell‐mediated immunity in ITP remains incompletely defined. While most studies have focused on immune platelet destruction in the spleen, an additional possibility is that the antiplatelet antibodies can also destroy bone marrow megakaryocytes. To address this, we negated the effects of T cells by utilizing an in vivo passive ITP model where BALB /c mice were administered various anti‐αII b, anti‐β3 or anti‐GPI b antibodies or antisera and platelet counts and bone marrow megakaryocytes were enumerated. Our results show that after 24 hours, all the different antiplatelet antibodies/sera induced variable degrees of thrombocytopenia in recipient mice. Compared with naïve control mice, however, histological examination of the bone marrow revealed that only 2 antibody preparations (mouse‐anti‐mouse β3 sera and an anti‐ αII b monoclonal antibody (MWR eg30) could affect bone marrow megakaryocyte counts. Our study shows that while most antiplatelet antibodies induce acute thrombocytopenia, the majority of them do not affect the number of megakaryocytes in the bone marrow. This suggests that other mechanisms may be responsible for megakaryocyte abnormalities seen during immune thrombocytopenia.     

系统性红斑狼疮重症血小板减少患者血清对巨核祖细胞的影响

研究系统性红斑狼疮(SLE)合并重症血小板患者的血清对正常人巨核祖细胞增殖分化的影响。以12例SLE重症血小板减少患者为研究对象,12份正常骨髓单个核细胞,培养中分别加入患者血清或灭活补体的患者血清,免疫化学染色检测巨核细胞克隆形成单位(CFU-MK),流式细胞仪检测CD41+细胞数。结果是正常对照组骨髓CFU-MK集落数为(61.22±29.71)个/片,加入SLE重症血小板减少患者血清后减少为(29.44±23.35)个/片,P<0.05;加灭活补体血清后减少为(22.56±15.21)个/片,与正常对照相比P<0.05;灭活补体与否差异不显著,P>0.05。加入患者血清或灭活补体的血清后,CD41+细胞数由正常(2.30%±1.63%)分别减少为(1.15%±0.85%)和(1.07%±0.76%),与正常对照相比P<0.05;灭活补体与否差异不显著。SLE血小板正常但活动期病人的血清对正常人CFU-MK和CD41+细胞的生成均无显著抑制。提示SLE重症血小板减少患者血清能抑制正常人骨髓巨核祖细胞的增殖分化,这种抑制作用是非补体依赖性的。     

Thrombocytopenia in systemic lupus erythematosus: association with antiplatelet and anticardiolipin antibodies

Serum platelet bindable immunoglobulin G (SPbIgG) and anticardiolipin antibodies (ACA) have been assayed in SLE patients with (group A, n = 8) and without thrombocytopenia (group B, n = 8). Moreover, we studied the binding of serum IgG on platelet proteins using a Western blotting procedure. Increased levels of SPbIgG were found in all thrombocytopenic patients and in five cases of group B. A binding of serum IgG on platelet proteins (80 and 53 kDa) was seen in seven of eight thrombocytopenic patients and in only one case of group B. ACA were present in the serum of four patients in each group and a significant inhibition of ACA IgG by entire washed platelets was achieved in only two severe thrombocytopenic cases. These data suggest that participation of ACA to the platelet destruction can be evoked for a few SLE patients, whereas recognition of platelet protein determinants by lupus autoantibodies is necessary to the thrombocytopenia.     

The platelet volume-number relationship in patients infected with the human immunodeficiency virus

The pathophysiology of thrombocytopenia in the acquired immune deficiency syndrome has not been elucidated completely. Many findings in these patients are identical to those with immune thrombocytopenic purpura. However, recent findings in acquired immune deficiency syndrome patients including the effect of zidovudine on platelet count and the demonstration of ultrastructural changes and viral RNA in megakaryocytes, have suggested that the human immunodeficiency virus may directly infect megakaryocytes, and play a role in acquired immune deficiency syndrome-related thrombocytopenia. To investigate further the mechanism of decreased platelet counts in human immunodeficiency virus-infected patients, the platelet volume-number relationship and corresponding bone marrow findings in 34 patients infected with human immunodeficiency virus were studied. Parameters evaluated included platelet count and mean platelet volume; bone marrow cellularity, megakaryocyte number, and number and percentage of denuded megakaryocyte nuclei. Two thirds of the platelet counts were low, and of these 92% had an inappropriately low mean platelet volume. These individuals had a platelet-volume number relationship that is very similar to that seen in myelosuppressive disorders. In addition, more than 90% of the bone marrows from thrombocytopenic patients had either normal or decreased numbers of megakaryocytes. These observations provide additional evidence to support the hypothesis that the pathophysiology of human immunodeficiency virus-associated thrombocytopenia may be due, at least in part, to a direct effect on the megakaryocytes.     

Cytokine induction by circulating immune complexes and signs of in-vivo complement activation in systemic lupus erythematosus are associated with the occurrence of anti-Sjögren's syndrome A antibodies

Circulating immune complexes (IC) and levels of IC‐induced cytokines have been correlated with complement activation and autoantibody profiles in systemic lupus erythematosus (SLE). SLE sera were analysed concerning levels of immune complexes (IC), classical complement function and different antinuclear and anti‐C‐reactive protein (CRP) autoantibodies. Blood mononuclear cells from healthy donors were stimulated with isolated IC and production of interleukin (IL)‐10, IL‐6 and IL‐12p40 was measured. Functional experiments revealed that increased levels of IC‐induced cytokines were associated with both increased classical complement activation and the occurrence of anti‐Sjögren's syndrome A (SSA) and anti‐SSB but not other autoantibodies. Biochemical measurement of circulating IC showed that the degree of complement activation and the occurrence of anti‐SSA were synergistically associated with levels of circulating IC in SLE sera, as complement activation was a prerequisite for the enhancing effect of anti‐SSA. Anti‐CRP was associated with complement activation, but not with other autoantibodies. Our results indicate that anti‐SSA and possibly anti‐SSB antibodies influence IC formation and subsequent IC‐induced cytokine induction, and that they thereby participate in the inflammatory process in active SLE.     

Anti‐citrullinated glucose‐6‐phosphate isomerase peptide antibodies in patients with rheumatoid arthritis are associated with HLA‐DRB1 shared epitope alleles and disease activity

To identify and characterize anti‐citrullinated glucose‐6‐phosphate isomerase (GPI) peptide antibodies in patients with rheumatoid arthritis (RA). Nine GPI arginine‐bearing peptides in human GPI protein were selected and cyclic citrullinated GPI peptides (CCG‐1–9) were constructed. Samples were obtained from RA (n = 208), systemic lupus erythematosus (SLE) (n = 101), Sjögren's syndrome (SS; n = 101) and healthy controls (n = 174). Antibodies against CCG‐1–9 were measured, and anti‐citrullinated α‐enolase‐1 (CEP‐1), ‐cyclic citrullinated peptides (CCP) and ‐GPI proteins antibodies were also examined. Patients with RA were genotyped for HLA‐DRB1. The numbers of shared epitope (SE) alleles were counted and compared with those of the autoantibodies. Rabbit GPI was citrullinated with rabbit peptidylarginine deiminase and immunoblot analysis of RA sera performed. The levels of autoantibodies were compared before and after treatment with TNF antagonists in 58 RA patients. Anti‐CCG‐2, ‐4 and ‐7 antibodies were detected in 25·5, 33·2 and 37·0% patients with RA, respectively, and these antibodies were very specific for RA (specificity, 98·1–99·7%). Altogether, 44·2, 86·1 and 13·9% of RA sera were positive for anti‐CEP‐1, ‐CCP and ‐GPI protein antibodies, respectively. Anti‐CCG‐2, ‐4 and ‐7 antibodies were correlated with anti‐CCP and anti‐CEP‐1 antibodies and with the presence of HLA‐DRB1 SE alleles. Citrullinated GPI protein was detected using RA sera. Treatment with tumour necrosis factor antagonists reduced significantly the levels of anti‐CCG‐2 and ‐7 but not of anti‐CEP‐1 antibodies. This is the first report documenting the presence of anti‐CCG antibodies in RA. Anti‐CCG‐2 and ‐7 antibodies could be considered as markers for the diagnosis of RA and its disease activity.     

Clinical application of anti double-stranded and single-stranded DNA antibodies measurements by enzyme-linked immunosorbent assay (ELISA) using E. coli plasmid DNA]

Anti double-stranded (ds) and single-stranded (ss) DNA IgG antibodies were detected in patients with various connective tissue diseases by RECOMBIGEN ELISA Anti ds-DNA Kit and ELISA Anti ss-DNA Kit (Nippon DPC Co) using E. coli plasmid DNA. High levels of anti ds-DNA and anti ss-DNA antibodies were mostly found and distributed in patients with systemic lupus erythematosus(SLE) and allied disorders. The sensitivity of Anti ds-DNA Kit was higher than that of current ELISA kit using calf thymus DNA antigen. In SLE patients with anti DNA antibodies sixty per cent of sera were reacted with both ds- and ss-DNA antigens, and forty per cent of sera were reacted only with ss-DNA antigen; there was no sample reacted positively with ds-DNA antigen alone. RECOMBIGEN ELISA Anti ds-DNA Kit and ELISA Anti ss-DNA Kit are highly sensitive and useful methods to detect anti ds- and/or ss-DNA IgG antibodies in patients with SLE.     

Preferential recognition of the phosphorylated major linear B-cell epitope of La/SSB 349-368 aa by anti-La/SSB autoantibodies from patients with systemic autoimmune diseases

Sera from patients with primary Sjögren Syndrome (pSS) or Systemic Lupus Erythematosus (SLE) often contain autoantibodies directed against La/SSB. The sequence 349–368aa represents the major B‐cell epitope of La/SSB, also it contains, at position 366, a serine aminoacid residue which constitutes the main phosphorylation site of the protein. In this study we investigated the differential recognition of the 349–368aa epitope and its phosphorylated form by antibodies found in sera from patients with systemic autoimmune diseases. Peptides corresponding to the sequence of the unphosphorylated (pep349–368aa) and the phosphorylated form (pep349–368aaPh) of the La/SSB epitope 349–368aa, as well as to a truncated form spanning the sequence 349–364aa and lacking the phosphorylation site (pep349–364aa), were synthesized. Sera from 53 patients with pSS and SLE with anti‐La/SSB specificity, 30 patients with pSS and SLE without anti‐La/SSB antibodies, 25 patients with rheumatoid arthritis and 32 healthy individuals were investigated by ELISA experiments. Autoantibodies to pep349–368aaPh were detected in sera of anti‐La/SSB positive patients with a higher prevalence compared to the pep349–368aa (66%versus 45%). Pep349–368aaPh inhibited the antibody binding almost completely (92%), while pep349–368aa inhibited the binding only partially (45%). Anti‐La/SSB antibodies presented a higher relative avidity for the phosphorylated than the unphosphorylated peptide. Immunoadsorbent experiments using the truncated peptide pep349–364aa indicated that the flowthrough showed a selective specificity for pep349–368aaPh, while the eluted antibodies reacted with both peptide analogues of the La/SSB epitope. These data suggest that sera from pSS and SLE patients with anti‐La/SSB reactivity possess autoantibodies that bind more frequently and with a higher avidity to the phosphorylated major B‐cell epitope of the molecule.     

Pathophysiology of HIV related thrombocytopenia: an analysis of 41 patients.

AIM--To analyse the pathogenic mechanism of HIV related thrombocytopenia. METHODS--Forty one patients with thrombocytopenia and HIV-1 infection were investigated over two years. Anticardiolipin antibodies were measured using an enzyme linked immunosorbent assay and antiplatelet antibodies were measured using an immunocapture technique. Tests for VDRL, C3 and C4, antinuclear antibodies and rheumatoid factor were also carried out in all patients and 80 control subjects (HIV-1 positive but non-thrombocytopenic). Indiumoxine labelled platelets were transfused in 13 patients. P24 antigen were also measured in 12 bone marrow aspirates. RESULTS--Antiplatelet antibodies and circulating immune complexes were found exclusively in the thrombocytopenic group; values for antiplatelet antibodies and circulating immune complexes were both higher in homosexual and bisexual patients. Three kinds of pattern were observed using 111 In-labelled platelets: splenic (n = 10); hepatic (n = 2); and destruction of bone marrow in just one case. The two most influential factors in the sequestration pattern were antiplatelet antibodies in the splenic uptake and circulating immune complexes in the hepatic and marrow sequestration. All patients, except three, had decreased platelet recovery. In those patients with a CD4 lymphocyte count of less than 200 x 10(6) cells/l the recovery was clearly greater (53%) than in patients who had more than 200 x 10(6) /l (28%). Finally, in seven of the 12 patients who were chosen for immunohistochemical study, p24 antigen was detected in the megakaryocytes, verifying that HIV-1 infects such cells. CONCLUSIONS--The pathogenic mechanism of HIV related thrombocytopenia is probably multifaceted. Antiplatelet antibodies and circulating immune complexes would cause peripheral destruction in the spleen, liver, and bone marrow, in that order; and, on the other hand, there would be an ineffective immune thrombopoiesis and direct infection of the megakaryocytes which could cause a change in the function and maturity of these cells.     

Autoantibodies to a specific peptide epitope of human Hsp60 (ATVLA) with homology to Helicobacter pylori HspB in H. pylori‐infected patients

Helicobacter pylori (Hp) may initiate autoimmunity as a result of molecular mimicry. The aim of this study was to compare the level of IgG antibodies to a specific epitope (P1 peptide) of human heat shock protein (Hsp)60 homologous to Hp Hsp60 (HspB) in the sera of healthy donors (HD), patients with Hp‐related gastritis or coronary heart disease (CHD), uninfected or with Hp infection confirmed by rapid urease test, histological examination (dyspeptic patients) the ¹³C urea breath test (¹³C UBT), and anti‐Hp antibodies (healthy donors, CHD patients). The Anti‐P1 IgG induction by Hp was verified by adsorption of sera with these bacteria and by experimental immunization of Caviae porcellus with Hp. Cytokine secretion by THP‐1Blue? monocytes in response to P1 was also assessed. Anti‐P1 antibodies were detected in patients with gastritis or CHD infected with Hp and they were not found in uninfected individuals or asymptomatic carriers. No antibodies were raised against P2 in any group. Reduced cross‐reactivity to P1 was exhibited by sera adsorbed with Hp. Caviae porcellus infected with Hp produced anti‐P1 autoantibodies. THP‐1XBlue? monocytes responded to P1 by production of proinflammatory cytokines. Autoantibodies against P1 in Hp‐positive patients with gastritis or CHD and upregulation of proinflammatory cytokines by P1 may contribute to the pathogenesis of Hp infection.     

Comparative analysis of autoantibodies targeting peptidylarginine deiminase type 4, mutated citrullinated vimentin and cyclic citrullinated peptides in rheumatoid arthritis: associations with cytokine profiles,clinical and genetic features

Antibodies against cyclic citrullinated peptides (anti‐CCP) are widely used for diagnosis of rheumatoid arthritis (RA). We performed a comparative analysis of antibodies targeting the citrullinating enzyme peptidylarginine deiminase type 4 (anti‐PAD4) and mutated citrullinated vimentin (anti‐MCV) with anti‐CCP autoantibodies in RA patients and examined their relationships with clinical parameters, cytokine profiles and the PADI4 gene. Autoantibodies were examined by enzyme‐linked immunosorbent assay (ELISA) in sera of 170 RA patients and 103 controls. Cytokine profiles were measured using a multiplex system. PADI4 polymorphisms (89G > A, 90T > C and 92G > C) were genotyped by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP). Anti‐PAD4, anti‐MCV and anti‐CCP autoantibodies were detected in 24, 61 and 74% of RA patients, respectively. Positive correlations were observed between anti‐PAD4 and disease duration; anti‐CCP and erythrocyte sedimentation rate (ESR); anti‐MCV and ESR and C‐reactive protein. Anti‐MCV antibodies were associated with high disease activity score 28 (DAS‐28) in early RA. Concentrations of T helper type 1 (Th1) [tumour necrosis factor (TNF)‐α, interleukin (IL)‐12, IL‐2, IL‐1β], Th2 (IL‐4, IL‐6, IL‐10, IL‐13) and Th17 (IL‐17) cytokines were higher in RA than in controls. Th2 and, to a lesser extent, Th1‐related cytokines, showed positive correlations with anti‐MCV and anti‐CCP. The GTG haplotype in PADI4 was associated with anti‐CCP and anti‐MCV, but not anti‐PAD4 antibodies. In conclusion, anti‐PAD4 antibodies are detected mainly in established RA, which is in contrast to the early detection of antibodies against citrullinated peptide/proteins (ACPAs). Among autoantibodies, anti‐MCV appear to perform better as markers of disease activity. Furthermore, anti‐CCP and anti‐MCV are associated genetically with the citrullinating enzyme PAD4 and are related strongly to Th1 and Th2 cytokines, suggesting a feed‐forward loop between cytokines and ACPA production.     

Plasma glycocalicin. An aid in the classification of thrombocytopenic disorders

In some patients with thrombocytopenia, it is difficult to determine whether the condition is caused by underproduction of platelets (reduced numbers of megakaryocytes) or an increase in the rate of their destruction (normal or increased numbers of megakaryocytes). A non-invasive test to help distinguish between these two categories of thrombocytopenia would be useful. We related the plasma concentration of glycocalicin, a fragment of the platelet-membrane glycoprotein Ib, to the mechanism of thrombocytopenia by evaluating bone marrow megakaryocyte content and measuring platelet life span. Plasma glycocalicin was measured with a monoclonal antibody to the glycocalicin component of platelet glycoprotein Ib. The mean (+/- SD) plasma concentration of glycocalicin in 34 healthy controls was 87 +/- 20 percent of the level in pooled normal plasma (range, 52 to 127 percent). All of eight patients with aplastic anemia or amegakaryocytic thrombocytopenia confirmed by examining bone marrow (in all patients) and by determining the life span of autologous platelets (in six patients) had glycocalicin levels significantly below the normal range (5 to 27 percent). In contrast, each of 25 patients with thrombocytopenia thought to be caused by a reduction in platelet life span, whose bone marrow contained normal or increased numbers of megakaryocytes, had glycocalicin levels that fell within or above the normal range (48 to 261 percent). There was no overlap of values between the two patient populations. These studies indicate that the measurement of plasma glycocalicin may be a useful adjunct in classifying thrombocytopenic disorders.     

Serum antibodies to human leucocyte antigen (HLA)‐E,HLA‐F and HLA‐G in patients with systemic lupus erythematosus (SLE) during disease flares: Clinical relevance of HLA‐F autoantibodies

T lymphocyte hyperactivity and progressive inflammation in systemic lupus erythematosus (SLE) patients results in over‐expression of human leucocyte antigen (HLA)‐Ib on the surface of lymphocytes. These are shed into the circulation upon inflammation, and may augment production of antibodies promoting pathogenicity of the disease. The objective was to evaluate the association of HLA‐Ib (HLA‐E, HLA‐F and HLA‐G) antibodies to the disease activity of SLE. The immunoglobulin (Ig)G/IgM reactivity to HLA‐Ib and β2m in the sera of 69 German, 29 Mexican female SLE patients and 17 German female controls was measured by multiplex Luminex^®‐based flow cytometry. The values were expressed as mean florescence intensity (MFI). Only the German SLE cohort was analysed in relation to the clinical disease activity. In the controls, anti‐HLA‐G IgG predominated over other HLA‐Ib antibodies, whereas SLE patients had a preponderance of anti‐HLA‐F IgG over the other HLA‐Ib antibodies. The disease activity index, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)‐2000, was reflected only in the levels of anti‐HLA‐F IgG. Anti‐HLA‐F IgG with MFI level of 500–1999 was associated with active SLE, whereas inactive SLE revealed higher MFI (>2000). When anti‐HLA‐F IgG were cross‐reactive with other HLA‐Ib alleles, their reactivity was reflected in the levels of anti‐HLA‐E and ‐G IgG. The prevalence of HLA‐F‐monospecific antibodies in SLE patients was also associated with the clinical disease activity. Anti‐HLA‐F IgG is possibly involved in the clearance of HLA‐F shed from lymphocytes and inflamed tissues to lessen the disease's severity, and thus emerges as a beneficial immune biomarker. Therefore, anti‐HLA‐Ib IgG should be considered as a biomarker in standard SLE diagnostics.     

Review: immune thrombocytopenic purpura: an update for immunohematologists

Immune thrombocytopenic purpura (ITP) is an acquired disease in which autoantibodies to platelets cause their sequestration and destruction by mononuclear macrophages, principally in the spleen. If increased production of platelets by megakaryocytes does not compensate for platelet destruction, the number of circulating platelets decreases (thrombocytopenia), resulting in a characteristic bleeding tendency (purpura). While most children with the disease experience a relatively short and benign clinical course, ITP in adults often lasts more than 6 months (chronic ITP) and is resistant to conventional treatment (corticosteroids, intravenous immune globulin, or splenectomy). The goal of medical management is to increase the platelet count to a safe level, without the risks of bacterial infections associated with splenectomy or toxicity from prolonged corticosteroid therapy. Splenectomy increases platelet counts in hours to days in most patients with acute ITP, but nearly 50 percent experience recurrent thrombocytopenia by 5 years postsplenectomy.     

Autoantibodies to PAD4 and BRAF in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes cartilage and bone destruction. The mechanisms leading to RA are unknown. There is currently no reliable cure for RA. Early treatment can reduce inflammation, joint damage and bone destruction. Thus, early diagnosis of RA is critical. However, definitive diagnosis of RA can be difficult. Immunologic tests that can be performed for the diagnosis of RA include detection of anti citrullinated protein antibodies (ACPAs). However, one third of RA patients have no ACPAs. To identify new autoantibodies in RA, we used the sera of RA patients to screen protein arrays containing 8000 human proteins. We found and validated two major autoantigens: PAD4 (peptidyl arginine deiminase 4) and BRAF (v raf murine sarcoma viral oncogene homolog B1) catalytic domain. We identified peptide targets of anti PAD4 and BRAF autoantibodies. We observed that anti PAD4 are inhibitory whereas anti BRAF stimulate BRAF activity. Anti PAD4 and anti BRAF antibodies may be used to diagnose RA, particularly in the absence of anti citrullinated protein antibodies.     

Increased prevalence of autoimmunity in Turner syndrome – influence of age

Individuals with Turner syndrome (TS) are prone to develop autoimmune conditions such as coeliac disease (CD), thyroiditis and type 1 diabetes (T1DM). The objective of the present study was to examine TS of various karyotypes for autoantibodies and corresponding diseases. This was investigated in a prospective cross‐sectional study of Danish TS patients (n = 107, median age 36·7 years, range: 6–60 years). A medical history was recorded and a blood sample was analysed for autoantibodies against gliadin, transglutaminase, adrenal cortex, intrinsic factor, anti‐thyroid peroxidase (anti‐TPO) and glutamic‐acid‐decarboxylase 65 (GAD‐65). Autoantibodies were present in 58% (n = 61) of all patients, whereof 18% (11) had autoantibodies targeting more than one organ. Patients with autoantibodies were significantly older than those without (P = 0·001). Anti‐TPO was present in 45% (48) of patients, of whom 33% (16) were hypothyroid. Overall, 18% (19) presented with CD autoantibodies, of whom 26% (five) had CD. Anti‐TPO and CD autoantibodies co‐existed in 9% (10). Immunoglobulin A deficiency was found in 3% (three) of patients, who all had CD autoantibodies without disease. Among four patients with anti‐GAD‐65 none had T1DM, but two were classified as having T2DM. One patient had adrenocortical autoantibodies but not adrenal failure. Autoantibodies against intrinsic factor were absent. Anti‐GAD‐65 was increased in isochromosomal karyotypes (3/23 versus 1/84, P = 0·008) with no other association found between autoantibodies and karyotype. In conclusion, TS girls and women face a high prevalence of autoimmunity and associated disease with a preponderance towards hypothyroidism and CD. Thus, health care providers dealing with this patient group should be observant and test liberally for these conditions even before clinical symptoms emerge.     

Guanine polynucleotides are self‐antigens for human natural autoantibodies and are significantly reduced in the human genome

In the course of investigating anti‐DNA autoantibodies, we examined IgM and IgG antibodies to poly‐G and other oligonucleotides in the sera of healthy persons and those diagnosed with systemic lupus erythematosus (SLE), scleroderma (SSc), or pemphigus vulgaris (PV); we used an antigen microarray and informatic analysis. We now report that all of the 135 humans studied, irrespective of health or autoimmune disease, manifested relatively high amounts of IgG antibodies binding to the 20‐mer G oligonucleotide (G20); no participants entirely lacked this reactivity. IgG antibodies to homo‐nucleotides A20, C20 or T20 were present only in the sera of SLE patients who were positive for antibodies to dsDNA. The prevalence of anti‐G20 antibodies led us to survey human, mouse and Drosophila melanogaster (fruit fly) genomes for runs of T20 and G20 or more: runs of T20 appear > 170 000 times compared with only 93 runs of G20 or more in the human genome; of these runs, 40 were close to brain‐associated genes. Mouse and fruit fly genomes showed significantly lower T20/G20 ratios than did human genomes. Moreover, sera from both healthy and SLE mice contained relatively little or no anti‐G20 antibodies; so natural anti‐G20 antibodies appear to be characteristic of humans. These unexpected observations invite investigation of the immune functions of anti‐G20 antibodies in human health and disease and of runs of G20 in the human genome.     

Diagnostic and prognostic values of anti glucose-6-phosphate isomerase antibodies in community-recruited patients with very early arthritis

The objective of this study was to determine the diagnostic and prognostic values of antiglucose‐6‐phosphate isomerase (GPI) antibodies in patients with very early arthritis. Anti‐GPI antibodies were measured by ELISA using purified GPI from rabbit muscle in: (i) 383 sera from healthy blood donors (n = 120), well‐established rheumatoid arthritis (RA) (n = 99) and non‐RA differentiated arthritis (NRADA) (n = 164) patients; (ii) 195 sera obtained from community‐recruited patients with very early inflammatory arthritis (VErA cohort) that were studied for 1 year and classified as having RA (n = 116), NRADA (n = 41), and undifferentiated arthritis (UA) (n = 38) after the follow‐up period. The criterion for severity was the progression of radiographic damage. Prevalence of anti‐GPI antibodies was significantly higher in well‐established RA patients (45·4%) compared to healthy subjects (2·5%). Anti‐GPI antibodies were also present in sera from NRADA: systemic lupus erythematosus 53%, polymyositis 45·4%, adult‐onset Still's disease 44%, systemic sclerosis 42·8%, spondylarthropathies 25% and primary Sjögren’s syndrome 5·8%. No significant association was found between the presence of anti‐GPI antibodies and the 3 diagnostic groups from the VErA cohort. No correlation was observed between anti‐GPI and autoantibodies usually associated with RA. Anti‐GPI antibodies were not predictive of radiological progression in patients with very early arthritis. Thus, anti‐GPI antibodies are not useful for discriminating RA from non‐RA rheumatic diseases and do not constitute a predictive factor of structural damage.     

Collagen autoantibodies in patients with vasculitis and systemic lupus erythematosus

In order to determine whether collagen autoantibodies are present in sera from patients with vascular diseases, a highly sensitive solid-phase radioimmunoassay was utilized to evaluate the presence of antibodies against collagen types I to VI and laminin in sera of 20 patients with vasculitis and 20 patients with systemic lupus erythematosus (SLE). Autoantibodies to interstitial collagen types I and II were noted in 20 and 35% of the patients, respectively. Most significantly, 70% of the polyarteritis nodosa patients and 55% of the total vasculitis group had autoantibodies to collagen type IV. In SLE, autoantibodies to collagen type V were detected in 70% and to collagen type IV in 85% of the patient sera. These data indicate that basement membrane and basement membrane-associated collagens may become immunogenic in patients with vasculitis and SLE. The role of these autoantibodies is most likely a result of endothelial damage secondary to the initial inflammatory disease process. However, it can be concluded from the present studies that collagen types IV and V are involved in the immune response and thereby may perpetuate further vascular damage.