The Immunological Role of the 1L-37/ IL-17 Axis in Patients with Rheumatoid Arthritis and Its Correlation with serum Vitamin D levels

This type of autoimmune disorder, which primarily causes joint disease, is known as rheumatoid arthritis (RA). In RA, significant joint damage leads to a gradual loss of cartilage, and as the disease progresses, bones may also be affected. Patients experience a wide range of symptoms, depending on the disease stage. Interleukin-17 and interleukin-37 play a vital role in the pathogenesis of rheumatoid arthritis, this study aimed to determine the levels of certain cytokines, such as interleukin-17 and interleukin-37, and to demonstrate the presence of low serum vitamin D levels in rheumatoid arthritis patients in Iraq. Samples were collected from an outpatient clinic at Baghdad Medical City Hospital and included 72 patients with rheumatoid arthritis (aged 23–65 years) in Baghdad between November 2025 and April 2026. The patients were distributed by sex: 59 females and 13 males. Control groups (35 individuals of varying ages) were also evaluated. The gender distribution in the sample was as follows: females (81.9%) and males (18.1%). Interleukin-17 (IL-17) levels were measured using ELISA in the blood of patients and control group members. Serum IL-17 and vitamin D levels were also measured. Results: The IL-17 level in patients was 16.53 ± 3.21 pg/mL, and in the control group, it was 9.31 ± 0.06 pg/mL. The difference between these two values was statistically significant (P<0.001). In contrast, the IL-37 level (14.20 ± 1.21 pg/ml for patients and 12.42 ± 2.13 pg/ml for control individuals) was statistically significantly higher (P = 0.001*), but the 25(OH)D level (15.79 ± 4.07 ng/ml) in our patients was much lower than the level obtained in the control group (36.94 ng/ml ± 7.98 ng/ml).