anti-P Antibodies Research Articles

Anti-ribosomal P protein autoantibodies from patients with neuropsychiatric lupus impair memory in mice.

To define whether anti-ribosomal P (anti-P) autoantibodies from patients with neuropsychiatric systemic lupus erythematosus (NPSLE) impair the function of hippocampal neurons that express the neuronal surface P antigen (NSPA) when accessing the brain via circulating blood. We used anti-P antibodies from patients with NPSLE and rabbit-generated anti-P and anti-NSPA antibodies. Primary hippocampal neurons from mice were analyzed to determine antibody cell surface binding (double immunofluorescence), intracellular calcium variations (Fura 2 AM), and apoptosis (caspase 3 activation). Hippocampal-dependent spatial flexible memory was assessed in mice subjected to a water maze test 24 hours after an intravenous injection of anti-P or anti-NSPA, using lipopolysaccharide (LPS) to permeate the blood-brain barrier. Presence of antibodies and apoptosis in the hippocampus was studied using immunohistochemistry and TUNEL assays. Hippocampal neurons expressed NSPA on the cell surface, as revealed by anti-P and anti-NSPA staining colocalization, and responded to both anti-P and anti-NSPA by exhibiting increased intracellular calcium levels. Neuronal apoptosis was induced when anti-P was directly injected by stereotaxis into the hippocampus or added to primary cultures. Upon LPS treatment, intravenously injected anti-P impaired memory but did not elicit neuronal apoptosis in the hippocampus, where it was detectable in low amounts. Anti-NSPA antibodies also impaired memory. Anti-P antibodies interact with NSPA on the surface of hippocampal neurons leading to apoptotic death or to functional perturbations, results that are likely dependent on the concentration of these antibodies. Circulating anti-P can access the hippocampus and impair memory without requiring neuronal death when the blood-brain barrier is disrupted. NSPA can mediate antibody-driven diffuse brain dysfunction, and anti-P might contribute to the cognitive impairment that is frequently observed in SLE.

Prosaposin overexpression following kainic acid-induced neurotoxicity.

Because excessive glutamate release is believed to play a pivotal role in numerous neuropathological disorders, such as ischemia or seizure, we aimed to investigate whether intrinsic prosaposin (PS), a neuroprotective factor when supplied exogenously in vivo or in vitro, is up-regulated after the excitotoxicity induced by kainic acid (KA), a glutamate analog. In the present study, PS immunoreactivity and its mRNA expression in the hippocampal and cortical neurons showed significant increases on day 3 after KA injection, and high PS levels were maintained even after 3 weeks. The increase in PS, but not saposins, detected by immunoblot analysis suggests that the increase in PS-like immunoreactivity after KA injection was not due to an increase in saposins as lysosomal enzymes after neuronal damage, but rather to an increase in PS as a neurotrophic factor to improve neuronal survival. Furthermore, several neurons with slender nuclei inside/outside of the pyramidal layer showed more intense PS mRNA expression than other pyramidal neurons. Based on the results from double immunostaining using anti-PS and anti-GABA antibodies, these neurons were shown to be GABAergic interneurons in the extra- and intra-pyramidal layers. In the cerebral cortex, several large neurons in the V layer showed very intense PS mRNA expression 3 days after KA injection. The choroid plexus showed intense PS mRNA expression even in the normal rat, and the intensity increased significantly after KA injection. The present study indicates that inhibitory interneurons as well as stimulated hippocampal pyramidal and cortical neurons synthesize PS for neuronal survival, and the choroid plexus is highly activated to synthesize PS, which may prevent neurons from excitotoxic neuronal damage. To the best of our knowledge, this is the first study that demonstrates axonal transport and increased production of neurotrophic factor PS after KA injection.

The association of serum anti-ribosomal P antibody with clinical and serological disorders in systemic lupus erythematosus: a systematic review and meta-analysis.

Anti-ribosomal P (anti-P) antibody is a serological specific marker of systemic lupus erythematosus (SLE). The aim of this study is to investigate the association of this antibody with clinical and serological disorders in SLE. All relevant literature was retrieved from PubMed, EMBASE, Web of Science and CNKI databases. The qualities of these studies were evaluated using a modified version of the Newcastle-Ottawa scale. The associations of anti-P antibody with clinical and serological disorders were determined by the pooled odds ratio (OR) and the confidence interval (CI) calculated using meta-analysis with the Mantel-Haenszel method. Sixteen cohort studies with 2355 patients were included in this study. Malar rash, oral ulcer and photosensitivity were strongly associated with serum anti-P antibody, with OR (95% CI) values of 2.05 (1.42-2.92), 1.49 (1.05-2.13) and 1.44 (1.08-1.91), respectively. Arthritis and renal involvement were not associated with anti-P antibody, whereas a high heterogeneity was observed due to ethnicity and publication bias, respectively. Neuropsychiatric SLE (NPSLE), hepatic involvement, anti-dsDNA, anti-Sm and anti-cardiolipinantibodies (aCL) were observed more frequently in anti-P positive patients than in negative patients. Studies on hepatic involvement showed a low precision with substantially broad CI (2.56-11.2). A high heterogeneity presented among studies on NPSLE, anti-Sm and aCL. Anti-P antibody is significantly associated with malar rash, oral ulcer, photosensitivity and serum anti-dsDNA antibody, and potentially associated with NPSLE, hepatic damage, serum anti-Sm and aCL.

Characterization of Anaphylaxis After Ecallantide Treatment of Hereditary Angioedema Attacks

Ecallantide is a human plasma kallikrein inhibitor indicated for treatment of acute attacks of hereditary angioedema for patients 12 years of age and older. Ecallantide is produced in Pichia pastoris yeast cells by recombinant DNA technology. Use of ecallantide has been associated with a risk of hypersensitivity reactions, including anaphylaxis. The objective of this detailed retrospective data review was to characterize anaphylaxis cases within the ecallantide clinical trials database. Potential cases of hypersensitivity reactions in the ecallantide clinical development program were identified by examining reported adverse events. The National Institute of Allergy and Infectious Disease criteria were used to identify those events that were consistent with anaphylaxis; these cases were then reviewed in detail. Results from investigational antibody testing also were examined. Among patients who received subcutaneous ecallantide (n= 230 patients; 1045 doses of 30 mg ecallantide), 8 patients (3.5%) had reactions that met the National Institute of Allergy and Infectious Disease criteria for anaphylaxis; none occurred on first exposure to the drug. All 8 reactions had symptom onset within 1 hour of exposure and cutaneous manifestations commonly observed in type I hypersensitivity reactions. All the reactions responded to standard management of type I hypersensitivity reactions and resolved without fatal outcomes. IgE antibody testing to ecallantide or P pastoris was not consistently positive in patients who experienced apparent type I hypersensitivity reactions. Anaphylaxis episodes after subcutaneous ecallantide exposure have clinical features suggestive of type I hypersensitivity reactions. However, anti-ecallantide or anti-P pastoris IgE antibody status was not found to be reliably associated with anaphylaxis.

Anti-N-methyl-D-aspartate receptor and anti-ribosomal-P autoantibodies contribute to cognitive dysfunction in systemic lupus erythematosus.

Autoantibodies against N-methyl-D-aspartate receptor (anti-NMDAR) and ribosomal-P (anti-P) antigens are potential pathogenic factors in the frequently observed diffuse brain dysfunctions in patients with systemic lupus erythematosus (SLE). Although studies have been conducted in this area, the role of anti-NMDAR antibodies in SLE cognitive dysfunction remains elusive. Moreover, the specific contribution of anti-P antibodies has not been reported yet. The present study attempts to clarify the contribution of anti-NMDAR and anti-P antibodies to cognitive dysfunction in SLE. The Cambridge Neuropsychological Test Automated Battery (CANTAB) was used to assess a wide range of cognitive function areas in 133 Chilean women with SLE. ANCOVA models included autoantibodies, patient and disease features. Cognitive deficit was found in 20%. Higher SLEDAI-2K scores were associated with impairment in spatial memory and learning abilities, whereas both anti-NMDAR and anti-P antibodies contributed to deficits in attention and spatial planning abilities, which reflect fronto-parietal cortex dysfunctions. These results reveal an association of active disease together with specific circulating autoantibodies, such as anti-NMDAR and anti-P, with cognitive dysfunction in SLE patients.

Selection and characterization of single-chain recombinant antibodies against phosphoprotein of newcastle disease virus

Phosphoprotein (P), involved in virus RNA replication and transcription, had become a new target for the research on treating Newcastle disease virus (NDV). Here we described the cloning and expression of phosphoprotein from NDV, and then screened the anti-P antibodies from the chicken single chain fragment variable (scFv) library, which were generated from chickens immunized with the ND vaccines. As a first step, the recombinant expression vector pET28a-P was successfully constructed. In a following step, two anti-P positive scFv clones from the scFv library were selected by indirect enzyme-linked immunosorbent assay (ELISA) method. The sequence analysis of two positive clones showed that there were more variation in complementary determine region (CDR) of VH and VL, and the CDR3 in VH exhibited a significant change in amino acid number and type. In another experiment, the purified scFv antibodies used in the assay was shown to be specific for NDV-P by western blot. The results indicated that the strategy we used in this experiment proved to be convenient way for screening scFv antibody, which paved a new way for the immunization diagnosis and the exploration of integrated control of NDV.

Anti-ribosomal-P antibodies in lupus nephritis, neuropsychiatric lupus, lupus hepatitis, and Chagas' disease: promising yet limited in clinical utility.

Anti-P antibodies have been associated with organ involvement in SLE, such as in autoimmune hepatitis, and have been suggested to be directly pathogenic. Neuropsychiatric lupus, lupoid hepatitis, autoimmune hepatitis, lupus nephritis, and Chagas' disease have been associated with the presence of anti-P antibody. This review seeks to look into the current literature on anti-P antibody and the association between SLE and non-SLE autoimmune connective tissue disorder.

Multicentric Prevalence Study of Anti-P Ribosomal Autoantibodies in Juvenile Onset Systemic Lupus Erythematosus Compared With Adult Onset Systemic Lupus Erythematosus

ObjectiveTo investigate the prevalence and associations with clinical manifestations of anti-P ribosomal antibodies in patients with juvenile-onset and adult-onset systemic lupus erythematosus (SLE). MethodsClinical and serological data of 30 patients with juvenile-onset SLE (age at onset younger than 16 years) were compared with data of 92 patients with adult-onset SLE. Symptoms occurring during the entire disease course were considered. Anti-P ribosomal antibodies were tested by ELISA. ResultsAnti-P ribosomal antibodies were found significantly more often in pediatric-onset SLE patients (26.7% vs 6.5%; OR=5.21 [95% CI=1.6–16.5], P=.003). Alopecia (OR=10.11, 95% CI=1.25–97) and skin rash (non-discoid) (OR=4.1, 95% CI=1.25–13.89) were significantly associated with anti-P ribosomal antibodies. ConclusionAnti-ribosomal P antibodies are more often found in patients with juvenile SLE. Alopecia and skin rash were the only clinical manifestations associated to anti-ribosomal P antibodies.

Competitive immunoassay of progesterone by microchip electrophoresis with chemiluminescence detection

A sensitive and rapid homogeneous immunoassay method based on microchip electrophoresis-chemiluminescence detection (MCE-CL) using luminol-hydrogen peroxide as chemiluminescence system catalyzed by horseradish peroxidase (HRP) was developed for the determination of progesterone (P). The assay was based on the competitive immunoreactions between HRP-labeled P antigen (HRP-P) and P with a limited amount of anti-P mouse monoclonal antibody (Ab), and MCE separation of free HRP-P and HRP-P-Ab immunocomplex followed by CL detection. The effect of various factors such as conditions for the CL reaction, MCE and incubation time for the immunoreactions were examined and optimized. Under optimal assay conditions, the MCE separation was accomplished within 80s. The linear range of detection for P was 8-800nM with a detection limit of 3.8nM (signal/noise ratio=3). This present method has been applied to determine P in human serum samples from normal and pregnant women. The result indicates that the proposed MCE-CL based homogeneous immunoassay method can serve as an alternative tool for clinical assay of P.

AB0720 Reduced olfaction and clinical significance in systemic lupus erythematosus

BackgroundSystemic lupus erythematosus (SLE) is an autoimmune disorder that affects 0.1% of the world population and central nervous system involvement in the disease neuropsychiatric SLE has been observed in 12–95%...

AB1199 Anxiety is associated with antiribosomal p antibody in childhood-onset systemic lupus erythematosus

ObjectivesTo investigate the prevalence of the anti-ribosomal P (anti-P) antibodies in childhood-onset systemic lupus erythematosus patients (cSLE) and to elucidate the association between anti-P and disease activity, laboratory and treatment...

ANTI-PHOSPHATIDYLSERINE ANTIBODIES IN ACUTE MYOCARDIAL INFARCTION

Acute Myocardial Infarction (AMI) is the combined result of environmental factors and personal predispositions. Many factors play a role in AMI in cluding anti-Phospholipid (aPL) antibodies, that may act in the induction of immunological response leading to the development of AMI. AntiPhosphatidylserine (PS) antibody is detected in var ious diseases like rheumatoid arthritis, systemic lupus erythematosus and anti-phospholipid antibody syndrome. The study of anti-PS antibody in AMI might shed light on etiologic mechanisms in the pat hogenesis of acute coronary syndromes. This study was conducted to evaluate whether prevalence of ant i-PS antibodies, in patients who had AMI and to analyze their relationship with traditional cardiov ascular risk factors. The prevalence of anti-PS IgG and IgM in a well characterized group of patients w ith AMI as a case group and in age and sex matched healthy subjects as control group. Sera fro m two groups were tested to evaluate the presence of IgG and IgM isotypes to anti-PS by ELISA method. The frequencies of positive test for anti-PS IgG were 26.70 and 8.90% among patients and controls re spectively with significant difference (p = 0.003). The anti-PS IgM frequencies were 12.20 and 1.10% in patients and the controls, with significant difference (p = 0.005). The findings of this study suggest that anti-PS antibodies seemed to play a ro le in AMI, independent risk factors for AMI, which may represent a link between autoimmunity and atherosclerosis in patients with AMI. Further studi es with bigger sample size including patients with AMI and healthy people are recommended to explore the exact role of anti-PS antibodies in AMI.

Higher Circulating Levels of Anti-Phosphatidylserine Antibody in Peptic Ulcer Patients Infected with CagA-Positive Strains of Helicobacter pylori

The CagA-positive strains of H. pylori were associated with the higher risk of peptic ulcer (PU) diseases. The aim of this study was to evaluate the serum concentrations of anti-phosphatidylserine (anti-PS) and anti-cardiolipin (anti-CL) antibodies in H. pylori-infected PU patients, H. pylori-infected asymptomatic (AS) carriers, and a healthy non-infected group and also to determine their correlation with the bacterial virulence factor CagA. A total of 100 H. pylori-infected PU patients (80 patients were positive for anti-CagA antibody and 20 patients were negative for anti-CagA antibody), 65 H. pylori-infected AS carriers (40 subjects were positive for anti-CagA antibody and 25 subjects were negative for anti-CagA antibody) and 30 healthy H. pylori-negative subjects (as a control group) enrolled in the study. Serum samples of participants were tested for the levels of anti-PS and anti-CL antibodies by ELISA. The mean serum levels of anti-PS antibody in the PU group (13.46 +/- 2.90 RU/mL) was significantly higher than that observed in the H. pylori-infected AS group (1.57 +/- 0.38 RU/mL, p < 0.001) and healthy uninfected control group (0.77 +/- 0.32 RU/mL, p < 0.001). No significant difference was observed for the mean serum levels of anti-PS antibody between the AS group and uninfected control group. In the PU group, the mean serum levels of anti-PS antibody was significantly higher in patients with a positive test for anti-CagA antibody (16.46 +/- 3.55 RU/mL) in comparison to patients with a negative test for anti-CagA antibody (2.74 +/- 1.29 RU/mL; p < 0.01). The differences of the mean serum levels of anti-CL antibody were not significant between PU, AS, and control groups. These results showed higher serum levels of anti-PS antibody in patients with PU disease, especially in those infected with the CagA+ strains of H. pylori. Clinical significance of the anti-PS antibody in H. pylori-infected PU patients can be considered in additional follow up studies.

Platelet protein S directly inhibits procoagulant activity on platelets and microparticles.

Anticoagulant plasma protein S (PS) is essential for maintaining haemostatic balance. About 2.5% of PS is stored in platelets and released upon platelet stimulation. So far, little is known about the functionality and importance of platelet (plt)PS. A platelet-associated protease cleaves plasma-derived (pd)PS and pltPS in the "thrombin-sensitive region", abolishing activated protein C (APC) cofactor activity. However, we showed that cleaved PS retains APC-independent anticoagulant activities ("PS-direct"). To investigate whether pltPS or pdPS exert PS-direct on platelets or platelet-shed microparticles, thrombin and factor (F)Xa generation on unstimulated or stimulated washed platelets and microparticles were measured. Western blotting revealed that pltPS and pdPS bound to washed, stimulated platelets and microparticles, and that pltPS had slower electrophoretic mobility than pdPS. Platelet stimulation in the presence of inhibitory anti-PS antibodies resulted in 2.6 ± 1.6-fold (p<0.0004, n=20) more thrombin generation upon addition of FXa and prothrombin. PltPS exerted PS-direct that was similar to or greater than that of Zn(2+)-containing pdPS and much greater than that of Zn(2+)-deficient pdPS. Findings were confirmed using purified pltPS. Platelet-bound pltPS and microparticle-bound pltPS had similar PS-direct. Finally, platelet stimulation in the presence of inhibitory anti-PS antibodies resulted in 1.5 ± 0.2-fold (p<0.0001, n=11) more FXa generation upon addition of TF/FVIIa and FX. Thus, pltPS inhibits both prothrombinase and extrinsic FXase activities. Neutralising antibodies against APC and TFPI had no effect on the PS-direct of pltPS or pdPS on platelets. This study indicates that pltPS may be an essential pool of PS that counterbalances procoagulant activities on platelets.

C0168 The APCR ratio is differently influenced by warfarin therapy when different assays are used

the onset of classical varicella zoster infectionwith an extensive purpuric rash covering both legs. The patient had leukocytosis with neutrophilia, thrombocytopenia (76.000X109/L), altered coagulation tests and DDimerN2000 ng/ml). Initially it was treated with broad-spectrum antibiotics, IV acyclovir and free fresh plasma (FFP). The lesions spread rapidly towards the abdomen forming painful ecchymotic plaques with necrotic-bullous areas and hypovolemic shock 48 hours after. Laboratory tests showed a disseminated intravascular coagulation (actived partial thromboplastinN180”, IQb10%, fibrinogenb0.5 g/l, D-Dimer 9000 ng/ml) and Hb 7.2 g/dl. She was treated with enoxaparin (1 mg/kg/12 h) and FFP (15–20 ml/kg). Subsequent result confirmed the diagnosis, as she had a free protein S (PS) of 6.1 IU/dl, total PS antigen 26.4 IU/dl and positive anti-PS antibodies (IgG 138 U/ml and IgM 28 IU/ml). After 22 days treatment, the girl had functional PS levels of 34%,with skin necrosis extended to 25% of the body surface. The patient required periodic surgery to remove necrotic tissue and skin graft. After 2 months of onset of treatment, the rate of PS reached normal levels (144%), with negative anti-PS antibodies. The patient required rehabilitation therapy to improve joint mobility and muscle mass in the lower extremities. At present, the functional recovery is complete. Comment: Purpura Fulminans secondary to varicella infection, mediated by antibodies against PS, is a rare entity. The severity and the extent of it will depend on the speed of the diagnosis and therapy. The clinical picture of PF is so characteristic that it is by itself diagnostic and should be suspected in any child with a rapidly progressive purpura and antecedents of chickenpox.FFP performance in terms of increased levels of PS, can be decreased by the presence of anti-PS antibodies. Treatment should be maintained until the disappearance of the anti-PS antibodies.

Prevalence and clinical significance of anti-ribosomal P antibody in childhood-onset systemic lupus erythematosus

To investigate the prevalence of the anti-ribosomal P (anti-P) antibodies in childhood-onset systemic lupus erythematosus patients (cSLE), healthy controls and first degree relatives. To elucidate the association between anti-P and disease activity, laboratory and treatment features in cSLE patients. We included consecutive SLE patients with disease onset before 16 years. Controls were age- and sex-matched. SLE patients were assessed for clinical and laboratory SLE manifestations, disease activity (SLE Disease Activity Index (SLEDAI)), damage (Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI)) and current drug exposures. Mood disorders were determined through Becks Depression and Becks Anxiety Inventory. Anti-P measured by enzyme-linked immunosorbent assay. We included 50 consecutive cSLE patients (mean age of 16.82 ± 3.46 years), 35 first degree relatives (mean age of 38.73 ± 3.89 years) and 20 health control (mean age of 18.3 ± 4.97 years). Anti-P was observed in 13 (26%) cSLE patients and in no first-degree relative (p < 0.01) or control (p < 0.01). Anti-P was more frequently observed in patients with anxiety (p < 0.002). No other clinical, laboratory or treatment features, including SLEDAI and SDI scores were associated with the presence of anti-P in cSLE patients. Anti-P is frequently observed in cSLE patients and was associated with the presence of anxiety in this cohort of cSLE.

Anti-phosphatidylserine, anti-cardiolipin, anti-β2 glycoprotein I and anti-prothrombin antibodies in recurrent miscarriage at 8–12 gestational weeks

To investigate the association of antibodies to β2-glycoprotein I (anti-β2GPI), cardiolipin (ACA), phosphatidylserine (anti-PS) and prothrombin (anti-PT) with recurrent spontaneous miscarriage (RSM). Case-control study involving 277 RSM cases and 288 controls: autoantibody levels were measured by ELISA. Differences between cases and controls were analyzed by nonparametric Mann-Whitney test, and logistic regression was used in analyzing the association of autoantibodies with RSM. Anti-PS IgG, ACA IgM and IgG, and anti-PT IgM were significantly associated with RSM risk, and differential antibody association was noted according to BMI and primary and secondary RSM. Higher prevalence of elevated anti-PS IgG was seen in cases, with the strongest risk above the 99th percentile. For ACA IgM, 28 cases (10.1%) and 5 controls (1.7%) were positive, with increasing OR for increasing cut-off points, which was significant at antibody titers >99th percentile. For ACA IgG, 101 cases (36.5%) and 13 controls (4.5%) were positive, with graded increase in OR for increasing cut-off points, which was significant at titers >90th percentile (maximal at titers >99th percentile). For anti-PT, 23 cases (12.0%) and 9 controls (6.1%) were positive, with increased OR at titers >90th percentile. Regression analyses confirmed the independent association of anti-PS IgG, ACA IgM and IgG with RSM, and significant RSM risk was associated with high anti-PS IgG (P<0.001) and ACA IgM (P<0.001) titers, and a dose-dependent increase in RSM risk was seen with progressively increased ACA IgG titers. No significant association existed between anti-PT IgM and RSM. Elevated ACA IgM and IgG, and anti-PS IgG antibodies are positively associated with RSM.

Role of toll like receptors in the antibody response to encapsulated bacteria

Encapsulated bacteria are major pathogens in humans. The capsular polysaccharides (PS) of these bacteria are T-independent type 2 antigens, are not processed by antigen presenting cells and do not induce T cell help. PS antigens are poor immunogens in children less than two years, the peak age incidence of encapsulated bacterial infection. The TNF family receptors BAFFR and TACI interaction with the cytokines BAFF and APRIL are essential co-stimulatory factors for humoral responses to PS. Linkage of PS to a carrier protein to make glycoconjugate vaccines, enhances the immune response to PS similar to a T cell dependent antigen. Multiple doses of glycoconjugate vaccines are required to elicit protection, making their use in the developing world problematic. TLR engagement augments BAFF mediated PS antibody responses and TLR ligands serve as adjuvants for induction of anti-PS antibodies either for pure PS or for PS-protein conjugate vaccines. A variety of TLR ligands stimulate increased production of antibodies directed to both PS and protein components of encapsulated bacteria, and glycoconjugate vaccines, suggesting their future role in immunization strategies.

Detection of serum anti-B/B' UsnRNP antibodies in patients with connective tissue diseases by immunoblotting

To investigate the reliability of the immunoblot method in the detection of serum immunoreactivity towards the B/B' polypeptides of U small nuclear ribonucleoproteins (UsnRNP) and to assess the significance of these antibodies in connective tissue disease (CTD) patients. We tested the sera of 348 patients with CTD (101 SLE, 51 systemic sclerosis, 53 primary Sjögren's syndrome, 27 poly/dermatomyositis, 15 rheumatoid arthritis and 101 overlap CTD), of 31 matched healthy subjects and 13 patients with primary Epstein-Barr virus (EBV) infection with high titre of IgG anti-EBV antibodies. IgG anti-UsnRNP antibodies were determined by immunoblotting on nuclear extract from Raji cells (an EBV-immortalised human B lymphoid cell line) and Jurkat cells (a human T lymphoid cell line). Anti-dsDNA antibodies were detected by indirect immunofluorescence on Crithidia luciliae and anti-ENA by counterimmunoelectrophoresis. Anti-dsDNA activity and avidity were measured in SLE sera by ELISA with Scatchard analysis. Results were statistically analysed by chi-square and Mann-Whitney tests. A high frequency of anti-B/B' antibodies was found in the sera of CTD patients, confined to SLE (54.4%) and overlap CTD with SLE features (55,2%). Anti-B/B' immune reactivity was closely associated with other anti-UsnRNP specificities, gel precipitating anti-nRNP and anti-P antibodies. Nine out of 15 (60%) anti-B/B' positive/anti-ENA negative lupus sera on Raji blots were confirmed to be positive also on Jurkat blots. The sera from patients with EBV infection provided, on Raji blots, completely different band patterns from those obtained with auto-immune sera. CONCLUSIONS. The Sm B/B' proteins are the predominant or, at least, the most frequently targeted antigens of the UsnRNP auto-immune response in SLE and "lupus-like" overlap CTD. Moreover, anti-B/B' is diagnostically specific for CTD with SLE features. Immunoblotting on human B lymphoid cells is a reliable method, in terms of sensitivity and specificity, for the detection of anti-Sm B/B' antibodies.

Anti-ribosomal P antibodies and lupus nephritis

Increasing attention has been paid to the relationship of autoantibodies to ribosomal P proteins (anti-P) with lupus nephritis. Several mechanisms of involvement of anti-P in lupus nephritis have been proposed, including cross-reactivity with anti-dsDNA and anti-endothelial cell antibodies (AECA). In addition, it is also suggested that anti-P might play a role in the development of lupus nephritis through induction of T helper 1 responses. Of note, recent studies have disclosed that the presence of isolated anti-P antibodies may discriminate patients with pure class V lupus nephritis, whereas the simultaneous presence of anti-dsDNA antibodies suggests class V disease with concomitant proliferative lesions. These observations lead to the hypothesis that anti-P and anti-dsDNA might result in membraneous changes and proliferative changes, respectively, although further investigation is required for confirmation.