Serum Level of Soluble Human Leukocyte Antigen G in Patients with Systemic Lupus Erythematosus and Rheumatoid Arthritis

Background: This study aimed to evaluate the serum level of human leukocyte antigen G [HLA-G] in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) compared to healthy controls; moreover, it attempted to assess its relationship with SLE and RA disease activity indices. Methods: This descriptive study was conducted on 31 SLE patients (17 cases with a recent diagnosis and 14 cases with a previous diagnosis), 21 RA patients (7 cases with a recent diagnosis and 14 cases with a previous diagnosis), and 18 healthy controls who visited Ghaem Hospital affiliated to Mashhad University of Medical Sciences, Mahhad, Iran. SLE and RA activity indices were measured and recorded. Furthemore, soluble isoforms, including shed HLA-G1 and HLA-G5, were measured in serum samples via the ELISA method. Results: A comparison of the five groups showed no significant differences in the serum level of sHLA-G. However, sHLA-G serum level was significantly higher in SLE and RA patients compared to healthy controls (P<0.05). sHLA-G level showed no correlation with disease duration and activity in SLE and RA patients (P>0.05). However, a strong positive correlation was observed between the serum level of sHLA-G and 24-h urine protein in the previously diagnosed SLE group (r=0.83, P=0.01). Conclusion: It seems that the serum level of sHLA-G is higher in RA and SLE patients compared to healthy controls. Furthermore, a strong correlation was found between sHLA-G serum levels and 24-h urine protein in cases with a previous diagnosis of SLE.