Association between the presence of anti-C1q antibodies and active nephritis in patients with systemic lupus erythematosus.

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE). A retrospective analysis was carried out on a group of 24 patients with SLE to evaluate whether the presence of anti-C1q antibodies (anti-C1q) is related to renal involvement and to explore the behaviour of anti-C1q with respect to LN during a four-year follow-up period. A first serum sample stored at the serum bank, taken not more than three years after SLE diagnosis and one serum sample per year for the subsequent four years were used to detect anti-C1q. Lupus clinical manifestations and serological markers of activity corresponding to the date of each serum sample selected were collected from medical records. In the first serum sample, anti-C1q were found in 8 active SLE. LN was confirmed by histology in 5/8 patients who were positive for anti-C1q and in 1/16 patients who were negative for these autoantibodies (p = 0.0069). Three patients (3/8) had anti-C1q without renal involvement but with lupus skin manifestation. Anti-C1q levels decreased in 3/5 patients with LN who responded to treatment and remained higher in 2/5 patients who needed a new renal biopsy which showed severe renal disease. The 15 patients without severe kidney disease and anti-C1q negative at diagnosis did not develop LN and anti-C1q remained negative in the 4 years of follow up. Anti-C1q were found in SLE patients with active renal involvement or with lupus skin disease. The absence of anti-C1q seemed to be linked to low probabilities of renal involvement. La nefritis lupica (NL) es una complicacion grave del Lupus Eritematoso Sistemico (LES). Se analizo retrospectivamente en 24 pacientes con LES si la presencia del anticuerpo anti-C1q (anti-C1q) se asociaba con NL y el comportamiento del anti-C1q respecto a la NL en un periodo de seguimiento de cuatro anos. El anti-C1q se determino en una primera muestra de suero no distante en mas de tres anos del diagnostico de LES y en una muestra por ano en los siguientes cuatro anos. Se obtuvo informacion de las historias clinicas, sobre manifestaciones clinicas de LES y marcadores serologicos de actividad para las fechas de seleccion de cada suero. En la primera muestra de suero se detecto anti-C1q en 8 pacientes con LES activo. NL fue confirmada por histologia en 5 de ellos y en uno de 16 pacientes con anti-C1q negativos (p = 0.0069); 3 de 8 pacientes fueron anti-C1q positivos sin NL y con lesiones en piel. Los niveles de anti-C1q disminuyeron en 3/5 pacientes con NL que respondieron al tratamiento y se mantuvieron aumentados en 2/5 que necesitaron una nueva biopsia, que evidencio compromiso renal grave. Los 15 pacientes sin enfermedad renal grave y con anti-C1q negativo al diagnostico no desarrollaron NL y el anti-C1q se mantuvo negativo en los 4 anos de seguimiento. El anti-C1q se asocio en pacientes con LES a NL activa o con compromiso en piel. La ausencia del anti-C1q pareceria relacionarse a un menor riesgo de desarrollar nefropatia lupica.