Complement receptor 1 (CR1) is a membrane protein mediating the transport of immune complexes (ICs) to phagocytes, and at least two polymorphisms on the CR1 gene are related to erythrocyte surface density of CR1 molecules, in turn related to the rate of IC clearance from circulation. The aim of the study was to explore whether the polymorphic sites of CR1 gene in exon 22 (His 1208 Arg), and exon 33 (Pro 1827 Arg), leading to amino acid change in the protein sequence are associated with systemic lupus erythematosus (SLE) susceptibility. To investigate this association, genomic DNA of 62 SLE patients and 76 healthy blood donors were genotyped by PCR-RFLP and direct sequencing. The CR1 analysis showed no significant association of the CR1 functional polymorphisms with SLE. However, the C/G genotype in Pro 1827 Arg polymorphism was significantly associated to nephritis and to the presence of cryoglobulins/ ICs compared to C/C and G/G genotypes (OR: 3.68, 95% confidence interval [CI], 1.028 - 13.2; p = 0.038 and OR: 16.6, 95% confidence interval [CI], 3.92 - 31.1; p=0.0002, respectively). This study indicates that the analysed polymorphisms of the CR1 gene do not appear to be primarily involved in the susceptibility of SLE. Nevertheless the Pro 1827 Arg polymorphism could constitute a risk factor of gravity of the disease.
Key words: Complement receptor 1, polymorphism, systemic lupus erythematosus, nephritis, cryoglobulins, immune complexes.
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