Mannose-binding lectin-low genotypes are associated with milder systemic and immunological disease expression in primary Sjögren's syndrome
1Department of Autoimmune Diseases, Laboratory of Autoimmune Diseases ‘Josep Font’, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and 2Department of Immunology, Hospital Clínic, Barcelona, Spain.
Correspondence to: M. Ramos-Casals, Department of Autoimmune Diseases, Hospital Clínic, Villarroel, 170, 08036-Barcelona, Spain. E-mail: mramos{at}clinic.ub.es
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Abstract |
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Objective. To investigate the association of mannose-binding lectin (MBL)-low genotypes with the clinical and immunological expression of primary SS.
Methods. Eighty-one patients with primary SS who fulfilled the 2002 classification criteria were included in the study. MBL2 polymorphisms were investigated by sequence-based DNA typing of the promoter and exon 1. Genotypes 0/0, 0/XA or XA/XA were considered as MBL-low and XA/A, A/0 and A/A as MBL-sufficient. Control groups included 46 patients who exclusively fulfilled the 1993 SS criteria, 114 SLE patients and 104 healthy individuals.
Results. Twelve (15%) SS patients had MBL-low genotypes, of whom six (7%) had genotype 0/XA, five (6%) had genotype 0/0 and one (1%) had genotype XA/XA. A higher prevalence of the XA/A genotype (32 vs 17%, P = 0.01) was found in primary SS patients in comparison with SLE patients. No patient with primary SS carrying MBL-low genotypes had purpura, glomerulonephritis or neurological involvement (0 vs 29%, P = 0.025). Immunologically, patients carrying MBL-low genotypes had a lower frequency of anti-Ro/SS-A antibodies (17 vs 55%, P = 0.014), anti-La/SS-B antibodies (8 vs 48%, P = 0.009) and low C4/C3 levels (0 vs 32%, P = 0.016). No patient with primary SS carrying the homozygous MBL-deficient genotype 0/0 had anti-Ro/SS-A or anti-La/SS-B antibodies, low C3/C4 levels or circulating cryoglobulins.
Conclusion. SS patients with MBL-low genotypes have a less pronounced systemic and immunological disease expression in comparison with those carrying MBL-sufficient genotypes. In primary SS, MBL deficiency may represent a protective factor against the development of more aggressive autoimmune damage.
KEY WORDS: Primary Sjögren's syndrome, Mannose-binding lectin, Gene polymorphism, Anti-Ro/SS-A antibodies, Innate immunity
Submitted 8 April 2008;
revised version accepted 22 September 2008.
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