RESUMEN
Levels of C4d, a fragment of C4 generated during activation of the classical complement pathway, were measured in the plasma of 77 patients with rheumatoid arthritis and 30 healthy subjects. Disease activity was judged according to Ritchie's articular index to be mildly active in 31 (group 1), moderately active in 29 (group 2), and severely active in 17 patients (group 3). Plasma levels of C3d, a fragment of C3, and serum levels of C4, C3, and immune complexes were also measured. The ratios C4d/C4 and C3d/C3 were calculated. The C4d/C4 and C3d/C3 ratios and the levels of circulating immune complexes correlated with the degree of disease activity without significantly departing from linear trend and discriminated between patients with different grades of disease activity. C4d, C3d, C4, and C3 also correlated with disease activity but in a non-linear relationship. A significant correlation was found between C4d and C3d, and between C4d/C4 and C3d/C3. C4d and C4d/C4 also correlated with circulating immune complexes. These results indicate that indices of C4 and C3 activation, in particular the ratios C3d/C3 and C4d/C4, provide a sensitive assessment of disease activity in rheumatoid arthritis, and confirm the major part played by the classical complement pathway in the pathogenesis of this disease.
Asunto(s)
Artritis Reumatoide/inmunología , Activación de Complemento , Complemento C4b , Vía Clásica del Complemento , Adulto , Anciano , Complejo Antígeno-Anticuerpo/análisis , Complemento C3/análisis , Complemento C3d , Complemento C4/análisis , Femenino , Humanos , Masculino , Persona de Mediana Edad , Fragmentos de Péptidos/análisisRESUMEN
Levels of C4d, a fragment of C4 generated during activation of the classical complement pathway, were measured in the plasma of 48 patients with systemic lupus erythematosus, 11 with inactive (group 1), 23 with mildly active (group 2), 14 with moderately/severely active disease (group 3), and 30 healthy subjects. Levels of C3d, C4, and C3 were also measured and the C4d/C4 and C3d/C3 ratios calculated. C4d levels correlated with the degree of disease activity, being higher in group 3 than in group 2, in group 2 than in group 1, and in group 1 than in controls. C4d/C4 gave a similar result. Activation indices of the common complement pathway, C3d and C3d/C3, also correlated with disease activity, but in a non-linear relationship, failing to discriminate between patient groups. C4 and C3 showed no correlation with disease activity. These results indicate that indices of C4 activation, C4d and C4d/C4, provide a laboratory measure of disease activity in lupus patients, for whom an objective assessment of the severity of the disease is not readily available.
Asunto(s)
Activación de Complemento , Complemento C4/análisis , Complemento C4b , Lupus Eritematoso Sistémico/inmunología , Fragmentos de Péptidos/análisis , Adulto , Anciano , Complemento C3/análisis , Complemento C3d , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
A new laser nephelometric technique for the measurement of the alternative complement pathway fragment Ba has been developed. Activation of the alternative complement pathway was assessed in 16 patients with Gram negative bacteraemia, six with Gram positive bacteraemia, 20 with rheumatoid arthritis, and 18 healthy subjects. Patients with Gram negative bacteraemia had significantly higher values of Ba (median 14.8%) than controls (9.3%) (p less than 0.01), while patients with Gram positive bacteraemia and rheumatoid arthritis had values similar to those of controls (10.1% and 9.5%). The technique proved sensitive and precise, and is suitable for the routine laboratory evaluation of complement activation through the alternative pathway.