RESUMEN
OBJECTIVE: To evaluate the relationship between the presence of different HLA-DRB1 genes and predisposition to develop a sporadic form of ankylosing spondylitis (AS) in a demographically well-defined population. METHODS: One hundred fifteen selected patients with sporadic (non-familial) forms of AS from six different cities and 748 bone marrow donors as control group. All individuals were typed for HLA-B27 by flow cytometry with monoclonal antibodies and PCR -SSP, as well as for HLA-DRB using the Dynal ELI SSO HLA-DRB Test (Dynal AS, Oslo, Norway). The Inno-Lipa DRB Decoder (Innogenetics NV Zwijndrecht, Belgium), was used for high-resolution HLA-DRB typing. RESULTS: The presence of the DRB1*01 antigen in the studied population is significantiy higher in B27 positive healthy individuals (bone marrow donors) than in B27 positive AS patients; also, DRB1*01 is higher in B27 negative AS patients than 827 negative controls. The frequency of DRB1*03 is higher in B27 negative controls than B27 negative AS patients. CONCLUSION: The results of this study suggest that DRB1*01 antigens might be involved in the development of sporadic forms of ankylosing spondylitis in HLA-B27 negative individuals in the studied area.