A DYSFUNCTIONAL ALLELE OF THE MANNOSE-BINDING PROTEIN GENE ASSOCIATESWITH SYSTEMIC LUPUS-ERYTHEMATOSUS IN A SPANISH POPULATION

Objective. To determine dysfunctional mannose binding protein (MBP) st atus of Spanish patients with systemic lupus erythematosus (SLE) and t o determine whether MBP and complement C4 null alleles contribute in a n additive way to SLE susceptibility. Methods. The frequencies of MBP alleles (characterized by polymorphisms at codon 54 and codon 57 of ex on 1) were determined by the amplification refractory mutation system- polymerase chain reaction in 50 Spanish patients with SLE and 49 match ed controls. Mutant genotypes for the codon 54 mutation were confirmed using a Ban I restriction enzyme digest method. Complement C4 allotyp ing was achieved by agarose gel electrophoresis of neuraminidase/carbo xypeptidase B digested plasma samples followed by immunofixation and s taining. Results. At least one dysfunctional MBP allele, unable to act ivate complement, was present in 52% of patients with SLE and in 31% o f controls (OR=2.4, 95% CI 1.1-5.6). Complement C4 null alle les (eith er C4A or C4B) were present in 61% of patients and 43% of controls (OR =2.1, 95% CI 0.9-4.9). A dysfunctional MBP allele and C4 null allele w ere present in 41% of patients and 16% of controls (OR=3.2, 95% CI 1.2 -8.1). Conclusion. The presence of a dysfunctional MBP allele is a ris k factor for developing SLE in this Spanish population and may affect susceptibility in an additive way with C4 null alleles.