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Mannan-binding lectin and complement C4A in Icelandic multicase families with systemic lupus erythematosus
  1. S Saevarsdottir1,*,
  2. H Kristjansdottir2,
  3. G Grondal2,
  4. T Vikingsdottir1,
  5. K Steinsson2,
  6. H Valdimarsson1
  1. 1Department of Immunology, Landspitali University Hospital, Reykjavik, Iceland
  2. 2Center for Rheumatology Research, Landspitali University Hospital
  1. Correspondence to:
    H Valdimarsson
    Department of Immunology, Landspitali University Hospital, 101 Reykjavik, Iceland; helgiv{at}landspitali.is

Abstract

Objective: To determine whether low mannan-binding lectin (MBL) and C4A null alleles (C4AQ0) are associated with systemic lupus erythematosus (SLE) in multicase families with SLE.

Methods: Low MBL level was determined by measuring serum levels and by genotyping for mutant structural (B/C/D, designated as 0) and promoter (LX) alleles (by real-time polymerase chain reaction). C4AQ0 was detected by protein electrophoresis and corroborated with haplotype and genotype analysis. In nine Icelandic families, 24 patients with SLE were compared with 83 first-degree and 23 second-degree relatives without SLE. Twenty four unrelated family members and a population group of 330 Icelanders served as controls.

Results: Overall, the frequency of low MBL genotypes (0/0, LX/0 and wild-type/0) tended to be higher in patients with SLE than in their first-degree and second-degree relatives (p = 0.06), but the frequency was similar in the families and in the controls (p = 0.6). The frequency of C4AQ0 was, however, increased in patients and their relatives compared with that in the controls (p = 0.04). The combination of low MBL genotypes and C4AQ0 was found more often in the patients than in their relatives (p = 0.03) and controls (p = 0.02). However, low MBL level was observed only in patients and first-degree relatives in five of the nine multicase families. In these five families, patients with SLE had low MBL genotypes more often (64%) than their first-degree (38%) and second-degree (0%) relatives (p = 0.001), and the patients with SLE also had, accordingly, lower MBL levels than their relatives (p = 0.001).

Conclusions: These findings indicate that low MBL levels can predispose people to SLE and highlight the genetic heterogeneity of this disease.

  • ANOVA, analysis of variance
  • MBL, mannan-binding lectin
  • SLE, systemic lupus erythematosus

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Footnotes

  • * Current address: Rheumatology Unit, Karolinska University Hospital, Stockholm, Sweden.

  • Published Online First 26 January 2006

  • Funding: This study was supported by grants from The Icelandic Research Fund for Graduate Students, The Science Fund of Landspitali University Hospital, and the Research Fund, University of Iceland.

  • Competing interests: None.

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