Objective -Antiphospholipid antibody (aPL) specificity for aPL-related events was evaluated in systemic lupus erythematosus (SLE). Methods-A study was carried out on 105 patients affected with SLE comparing the prevalence of lupus anticoagulant (LA) and IgG and IgM anticardiolipin antibodies (aCL) between patients with and without features of antiphospholipid syndrome (APS). Antiphospholipid antibody profile was subsequently evaluated in the aPL positive patients with and without aPL-related events, thus excluding the patients with complications of APS possibly due to factors other than aPL.
Serum reactivities towards individual U1 snRNP proteins were determined by immunoblotting in 32 patients with mixed connective tissue disease (MCTD). Time persistence of immunoblot profiles and clinical significance of anti-(U1)RNP antibody specificities were also investigated. IgG anti-(U1)RNP antibodies were found in the sera of 29 out of 32 patients (90.6%): 21 (65.6%) reacted with the 70-kD protein, 25 (78.1%) with A, 23 (71.9%) with C and 20 (62.5%) with B/B' proteins. None were reactive with the Sm-D peptide. Seventy kilodalton antibody specificity was strongly associated with a higher antinuclear antibody titre (> 160) and slightly associated with disease activity; anti-B/B' specificity was associated with lymphadenopathy. Anti-A, -C and -B/B' antibodies were negatively associated with systemic lupus erythematosus (SLE) skin rashes. Two types of anti-(U1)RNP blotting patterns were selected: "full spectrum" (53.1% of cases) and a "partially/no reactive" one (46.9%). Such patterns were unchanged over time in 14 out of 16 cases prospectively examined (87.5%), while the pattern shifted from "full spectrum" to "partially/no reactive" in 2 cases (12.5%): in 1 after a prolonged clinical remission (> or = 4 years) and in the other following immunosuppressive therapy. The anti-(U1)RNP antibody immunoblot profile in MCTD patients consisted of various reactivities and remained unchanged over time in most cases. Antibody reactivity against the 70-kD protein represented the major U1 snRNP specificity. The various anti-(U1)RNP specific reactivities demonstrated poor clinical significance within MCTD. Thus, MCTD seems to be characterized by a longstanding serological heterogeneity whose reactivities do not apparently correspond to distinct features within the broad clinical spectrum of MCTD.
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