Serum levels of beta 2-microglobulin in HLA-B27+ patients with acute anterior uveitis and ankylosing spondylitis

Serum Levels of Beta-2 Microglobulin in Rheumatoid Arthritis Patients and its Relationship with Disease Activity: Can it be used as a Disease Activity Marker?

Background Beta-2 microglobulin (β2M) is mainly released from activated lymphocytes. Increased serum β2M levels have been shown in autoimmune diseases. The aim of this study was to analyse the serum levels of β2M in rheumatoid arthritis (RA) patients and to evaluate its relationship with disease activity measures.

Material and Methods This cross-sectional study included 137 RA patients, 102 ankylosing spondylitis patients (AS) and 50 healthy controls (HC). To assess the disease activity of RA patients, the 28-joint Disease Activity Score-Erythrocyte Sedimentation Rate (DAS28-ESR), the 28-joint Disease Activity Score-C-Reactive Protein (DAS28-CRP), the Simplified Disease Activity Index (SDAI) and the Clinical Disease Activity Index (CDAI) were used. A p value of <0.05 was considered statistically significant.

Results Serum β2M levels were significantly higher in RA patients (2.95±1.19 mg/L) compared with HC (2.21±0.54 mg/L) and AS patients (2.200.58 mg/L) (p<0.001). There was a statistically significant correlation between β2M levels and DAS28-ESR (rs=0.359, p<0.001), DAS28-CRP (rs=0.293, p=0.001), SDAI (rs=0.332, p<0.001) and CDAI (rs=0.291, p=0.001). Serum β2M levels were higher in the RA group with DAS28-ESR ≥3.2 (3.30±1.42 mg/L) than in the DAS28-ESR <3.2 group (2.67±0.87 mg/L) (p=0.002).

Conclusion Our study revealed that serum β2M levels were higher in RA patients than in healthy controls, and, in contrast to other studies, we found positive correlations between β2M levels and RA disease activity measures.

Ankylosing spondylitis: a beta2m-deposition disease?

To explain the strong association between HLA-B27 and ankylosing spondylitis, we suggest that the release of beta(2)-microglobulin (beta(2)m) from a subpopulation of cell surface-expressed HLA-B27 molecules leads to beta(2)m-deposition within synovia and to the initiation of an inflammatory process, which culminates in destructive spondyloarthropathy.