RESUMEN
DNA-dependent protein kinase (DNA-PK) consists of a DNA binding subunit (Ku autoantigen), and a catalytic subunit (DNA-PKcs). In the present study, human autoantibodies that recognize novel antigenic determinants of DNA-PK were identified. One type of autoantibody stabilized the interaction of DNA-PKcs with Ku and recognized the DNA-PKcs -Ku complex, but not bio-chemically purified DNA-PKcs. Another type recognized purified DNA-PKcs. Autoantibodies to Ku (p70/p80 heterodimer), 'stabilizing' antibodies, and antibodies to DNA-PKcs comprise a linked autoantibody set, since antibodies recognizing purified DNA-PKcs were strongly associated with stabilizing antibodies, whereas stabilizing antibodies were strongly associated with anti-Ku. This hierarchical pattern of autoantibodies specific for components of DNA-PK (anti-Ku > stabilizing antibodies > anti-DNA-PKcs) may have implications for the pathogenesis of autoimmunity to DNA-PK and other chromatin particles. The data raise the possibility that altered antigen processing and/or stabilization of the DNA-PKcs-Ku complex due to autoantibody binding could play a role in spreading autoimmunity from Ku to the weakly associated antigen DNA-PKcs.
Asunto(s)
Antígenos Nucleares , Autoanticuerpos/fisiología , Autoantígenos/inmunología , Autoantígenos/metabolismo , ADN Helicasas , Proteínas de Unión al ADN/inmunología , Proteínas de Unión al ADN/metabolismo , Proteínas Nucleares/inmunología , Proteínas Nucleares/metabolismo , Proteínas Serina-Treonina Quinasas/inmunología , Proteínas Serina-Treonina Quinasas/fisiología , Reacciones Antígeno-Anticuerpo , Autoanticuerpos/sangre , Autoanticuerpos/química , Autoantígenos/química , Enfermedades Autoinmunes/inmunología , Enfermedades Autoinmunes/metabolismo , Catálisis , Fenómenos Químicos , Química Física , ADN/inmunología , Proteína Quinasa Activada por ADN , Proteínas de Unión al ADN/química , Histonas/inmunología , Humanos , Sueros Inmunes/química , Immunoblotting , Autoantígeno Ku , Proteínas Nucleares/química , Pruebas de Precipitina , Proteínas Serina-Treonina Quinasas/químicaRESUMEN
The frequent coexistence of anti-Ro and anti-La autoantibodies is well described, however, there is little evidence of sequential development of these two autoantibodies. We report a case of typical Sjogren's syndrome with high titer anti-Ro antibodies, who subsequently developed anti-La antibodies later in the course. This case suggests that the anti-La antibodies may actually follow the anti-Ro antibodies in some cases as hypothesized in the concept of linked set of autoantibodies, analogous to development of anti-Sm in certain anti-nRNP antibody positive SLE patients and animal models.
Asunto(s)
Anticuerpos Antinucleares/biosíntesis , Autoantígenos/inmunología , Enfermedades Autoinmunes/inmunología , Ribonucleoproteínas/inmunología , Síndrome de Sjögren/inmunología , Anticuerpos Antinucleares/sangre , Anticuerpos Antinucleares/inmunología , Especificidad de Anticuerpos , Femenino , Humanos , Persona de Mediana Edad , Factores de Tiempo , Antígeno SS-BRESUMEN
The Ul small nuclear ribonucleoprotein (snRNP), a complex of nine proteins with Ul RNA, is a frequent target of autoantibodies in human and murine systemic lupus erythematosus (SLE). Anti-Sm antibodies recognizing the B'/B, D, E, F, and G proteins of Ul snRNPs are highly specific for SLE, and are nearly always accompanied by anti-nRNP antibodies recognizing the Ul snRNP-specific 70K, A, and/or C proteins. Previous studies suggest that human anti-nRNP antibodies recognize primarily the U1-70K and Ul-A proteins, whereas recognition of Ul-C is less frequent. We report here that autoantibodies to U1-C are more common in human autoimmune sera than believed previously. Using a novel immunoprecipitation technique to detect autoantibodies to native Ul-C, 75/78 human sera with anti-nRNP/ Sm antibodies were anti-Ul-C (+). In striking contrast, only 1/65 anti-nRNP/Sm (+) MRL mouse sera of various Igh allotypes was positive. Two of ten anti-nRNP/Sm (+) sera from BALB/c mice with a lupus-like syndrome induced by pristane recognized Ul-C. Thus, lupus in MRL mice was characterized by a markedly lower frequency of anti-U1-C antibodies than seen in human SLE or pristane-induced lupus. The results may indicate different pathways of intermolecular-intrastructural diversification of autoantibody responses to the components of Ul snRNPs in human and murine lupus, possibly mediated by alterations in antigen processing induced by the autoantibodies themselves.
Asunto(s)
Autoanticuerpos/sangre , Enfermedades Autoinmunes/sangre , Enfermedades Autoinmunes/inmunología , Lupus Eritematoso Sistémico/inmunología , Ribonucleoproteína Nuclear Pequeña U1/inmunología , Animales , Anticuerpos Monoclonales , Complejo Antígeno-Anticuerpo , Autoanticuerpos/aislamiento & purificación , Línea Celular , Humanos , Immunoblotting , Alotipos de Inmunoglobulinas , Lupus Eritematoso Sistémico/sangre , Ratones , Ratones Endogámicos BALB C , Ratones Mutantes , Ribonucleoproteína Nuclear Pequeña U1/aislamiento & purificación , Células Tumorales CultivadasRESUMEN
Autoantibodies to RNA polymerases (RNAP) I and III are highly specific for scleroderma (SSc), whereas autoantibodies to RNAP II are associated with systemic lupus erythematosus (SLE) and overlap syndromes, as well as SSc. The specificities of autoantibodies to RNAP I, II, and III in 129 SSc sera were investigated in the present study. Immunoprecipitation and pulse-chase analysis demonstrated several patterns of autoantibody recognition of RNAPs. Some sera immunoprecipitated RNAP II only after its largest subunit was phosphorylated, suggesting that they contained autoantibodies that recognized an epitope carrying a phosphoamino acid. Autoantibody recognition of all three classes of RNAPs was influenced strongly by race. Although in SLE, autoantibodies to the phosphorylated form of RNAP II (RNAP IIO) were identified in all races, in SSc, these autoantibodies were seen in 21% of Japanese and 5% of Black patients, but never in Caucasians. A striking association of anti-RNAP IIO with anti-topoisomerase I (topo I) autoantibodies was found in Japanese and Black SSc, but not SLE, patients. However, anti-topo I Abs were not associated with anti-RNAP IIO in Caucasians. Japanese SSc patients who were positive for both anti-RNAP IIO and anti-topo I Abs had a significantly higher frequency of diffuse disease, pigmentation changes, flexion contractures, and acro-osteolysis than patients having autoantibodies to topo I alone, and were diagnosed at a younger age (p < 0.05). These data suggest that genetic factors (possibly HLA-linked) influence autoantibody specificity, and that different autoantibody fine specificities may either cause, or be predictive of, different clinical outcomes.
Asunto(s)
Autoanticuerpos/sangre , ADN-Topoisomerasas de Tipo I/inmunología , ARN Polimerasa II/inmunología , Esclerodermia Sistémica/inmunología , Adulto , Pueblo Asiatico , Población Negra , Femenino , Humanos , Japón/epidemiología , Lupus Eritematoso Sistémico/inmunología , Masculino , Persona de Mediana Edad , Fosforilación , Pruebas de Precipitina , ARN Polimerasa II/química , Esclerodermia Sistémica/epidemiología , Población BlancaRESUMEN
Autoantibodies to RNA polymerases (RNAP) I, II, and III are reported to be highly specific for the diagnosis of scleroderma (systemic sclerosis, SSc). In the present study, the specificity of autoantibodies to RNAP I and III for SSc was confirmed by immunoprecipitation of 35S-labeled proteins. However, we report here the previously unrecognized production of anti-RNAP II autoantibodies by 9-14% of patients with SLE and mixed connective tissue disease/overlap syndrome. 12 out of 32 anti-RNAP II positive sera (group 1) immunoprecipitated a diffuse 220-240-kD band identified as the largest subunit of RNAP II whereas the remaining 20 (group 2) immunoprecipitated preferentially the 240-kD phosphorylated (IIo) form of the large subunit. After pulse labeling, group 1 sera immunoprecipitated only the 220-kD (IIa) RNAP II subunit, whereas the diffuse IIa/IIo band plus the 145-kD second largest RNAP II subunit (IIc) were immunoprecipitated after several hours of cold chase, suggesting that these sera recognized primarily the largest subunit of RNAP II. Group 2 sera recognized the IIc subunit after pulse labeling, and immunoprecipitated the IIc and IIo, but not the IIa, subunits after cold chase. Although it has been suggested that autoantibodies to RNAP II are usually accompanied by anti-RNAP I/III in SSc, all but one of the anti-RNAP II positive sera from SLE or mixed connective tissue disease/overlap syndrome patients, as well as most of the SSc sera, were negative for anti-RNAP I/III. Moreover, in contrast to previous reports suggesting that anti-RNAP antibodies rarely coexist with other SSc subset marker antibodies, anti-RNAP II antibodies were often accompanied by anti-Ku, anti-nRNP, or anti-topoisomerase I autoantibodies in the present study. We conclude that autoantibodies to RNAP II are not a specific marker for SSc, whereas autoantibodies to RNAP I/III are associated primarily with SSc. In addition, we have identified two distinctive patterns of RNAP II antigen recognition by autoantibodies, one of them characterized by specific recognition of the transcriptionally active (phosphorylated) form of RNAP II. The clinical significance of these different patterns remains to be determined.
Asunto(s)
Autoanticuerpos/sangre , Lupus Eritematoso Sistémico/inmunología , ARN Polimerasa II/inmunología , Adulto , Anciano , Fosfatasa Alcalina/farmacología , Humanos , Lupus Eritematoso Sistémico/etnología , Persona de Mediana Edad , Fosforilación , Pruebas de PrecipitinaRESUMEN
The Su autoantigen was characterized biochemically using human and murine autoimmune sera and the clinical significance of anti-Su antibodies was studied in 236 Japanese and 160 American patients with systemic rheumatic diseases. Anti-Su in immunodiffusion (ID) was strongly associated with immunoprecipitation of one or more 100- to 102-kDa proteins by MRL/lpr mouse sera (27/32 of ID positive vs 4/20 of ID negative, P = 0.000016), and all four human anti-Su reference sera immunoprecipitated the 100/102-kDa protein(s). In addition, all sera immunoprecipitated a less efficiently labeled approximately 200-kDa protein that comigrated on sucrose density gradients with the 100/102-kDa proteins. Based on these data, a complex of the 100/102-kDa and 200-kDa proteins is likely to be the main target of anti-Su antibodies. Three of four anti-Su monospecific sera were negative for immunofluorescent antinuclear antibodies (ANA), suggesting anti-Su antibodies may be associated with a negative ANA in some cases. Autoantibodies to Su were detected frequently by immunoprecipitation in systemic lupus erythematosus (17-21%), scleroderma (13-20%), and overlap syndrome (22-40%) and were associated with autoantibodies to Ku.