Soluble HLA-G in rheumatoid arthritis.

We investigated potential correlations between soluble HLA-G (sHLA-G) and soluble HLA class I (sHLA-I) levels, respectively, and parameters of disease activity or genetic factors determined by HLA-DRB1 and HLA-DQB1 in patients with rheumatoid arthritis (RA). SHLA-G plasma concentrations from 106 RA patients (mean age 59.8 years, 80 women) were assessed by a sensitive enzyme-linked immunosorbent assay format. The mean sHLA-G levels were lower and sHLA-I levels higher in the RA patients than in healthy controls. Correlation coefficients of 0.248 to 0.344 (p < 0.01) between sHLA-G and rheumatoid factor, CRP, and EULAR joint swelling score were found. Patients with disease-associated HLA epitopes had higher sHLA-G levels than those without. Significantly lower sHLA-G was observed in groups of patients having HLA-DRB1*03 or HLA-DQB1*02 compared to groups without these genotypes. In contrast, HLA-DQB1*03 or disease-associated epitopes combined with HLA-DQB1*03 were associated with higher sHLA-G levels, whereas the inverse was observed in the combined presence of HLA-DRB1*03 and HLA-DQB1*02. SHLA-G as a percentage of sHLA-I was lower in patients positive for HLA-DQB1*02 and higher in patients positive for HLA-DQB1*03 and in its combined presence with disease-associated epitopes or with HLA-DRB1*07. As especially sHLA-G strongly inhibits T and natural killer (NK) cell functions, low sHLA-G suggests that T and NK cell activities are not efficiently restricted by sHLA-G molecules in rheumatoid arthritis. The sHLA-G levels, however, increase in correlation with parameters of disease activity and appear to be affected by the presence of disease-predisposing epitopes and other HLA-DRB1, DQB1 genotypes.

Soluble HLA-DR levels in serum are associated with therapy and genetic factors in rheumatoid arthritis.

As rheumatoid arthritis (RA) is an HLA-DR associated autoimmune disease and soluble HLA-DR (sHLA-DR) molecules have the capacity to regulate the immune response, we studied the sHLA-DR levels in RA patients in view of therapy modalities and clinical and biologic parameters of disease activity. For this sHLA-DR concentrations from 87 RA patients were determined by a sensitive enzyme-linked immunoabsorbent assay (ELISA) format. There was a weak but significant correlation between sHLA-DR levels and disease activity (r 0.186 to 0.287, p < 0.004 to < 0.001). The mean serum sHLA were not significantly different between groups with or without corticosteroids, or undergoing therapy with different disease modifying antirheumatic drugs. However, patients treated with a combination of methotrexate and prednisolone have lower sHLA-DR (206 +/- 21 ng/ml, n = 34) compared with the mean value for all other samples (306 +/- 16, n = 217, p < 0.001). This corresponded with significantly lower EULAR pain and swelling scores, ESR and rheumatoid factor (RF) by latex fixation (p < 0.02 to 0.001) in the former, compared with the latter group. Furthermore, sHLA-DR was, respectively, 267 +/- 15 ng/ml (n = 182) in samples from patients treated with nonsteroidal anti-inflammatory drugs (NSAIDs), and 358 +/- 31 (n = 72) without NSAIDs (p < 0.01). Lower sHLA-DR with NSAIDs contrasted with significantly higher scores for pain, swelling, CRP, and RF by latex fixation and by Waaler-Rose test (p < 0.05 to 0.001). Comparison of subgroups with or without the shared epitope of RA disease (Q)R/KRAA within the HLA-DR beta1-chain confirmed significantly higher parameters of disease activity and sHLA-DR in the presence of this disease associated epitope in our patients. Different mechanisms appear to be involved in sHLA-DR production or release, as their level correlates positively with disease activity under combined therapy with corticosteroids and methotrexate, but decreases with higher disease activity in patients treated with NSAIDs.