In primary Sjögren's syndrome, HLA class II is associated exclusively with autoantibody production and spreading of the autoimmune response.

OBJECTIVE: To reevaluate, in a large series of patients with Sjögren's syndrome (SS) recruited from 2 French centers, the question of whether HLA is associated with SS itself or with a pattern of secretion of autoantibodies.
METHODS: One hundred forty-nine white patients fulfilling the American-European Consensus Group criteria for SS were divided into 3 subgroups, according to their anti-Ro/SSA and anti-La/SSB status, as follows: group 1 (n = 53), no antibody; group 2 (n = 46), anti-SSA only; group 3 (n = 50), both anti-SSA and anti-SSB. Patients were compared with 222 unrelated healthy subjects representative of the white population in France.
RESULTS: Comparisons between the 149 SS patients and 222 controls confirmed the association of SS with DRB1*03 (the frequency was 25% in patients versus 10% in controls) and DQB1*02 (32% versus 22%). The association between HLA and SS was restricted to patients with anti-SSA and/or anti-SSB; no association with HLA was observed in patients in group 1 (no antibody). The frequency of HLA-DRB1*15 was highest in group 2 (24%), compared with 11% in group 1 and 11% in controls, whereas the frequency of HLA-DRB1*03 was highest in group 3 (44%), compared with 12% in group 1, 19% in group 2, and 10% in controls. Group 2 and group 3 had more clinical and biologic markers of activity than did group 1 but were not clinically different. HLA alleles were not associated with clinical features of the disease, and were associated with only some biologic features: rheumatoid factor positivity, increased serum IgG, and thrombocytopenia were associated with HLA-DRB1*03, and neutropenia was associated with DQB1*01.
CONCLUSION: HLA class II markers confer genetic susceptibility to Sjögren's syndrome. The association between HLA and SS is restricted to patients with anti-SSA and/or anti-SSB antibodies; HLA is not associated with SS in patients without these autoantibodies. The absence of a difference in disease severity between groups 2 and 3, as well as the restricted association of HLA-DRB1*03 in group 3, strongly suggest that HLA alleles predispose to autoantibody secretion, without being associated with clinical outcome. HLA class II phenotype might support epitope spreading: HLA-DR15 favors anti-SSA synthesis, whereas HLA-DR3 is associated with both anti-SSA and anti-SSB production.