Rheumatoid arthritis (RA) is a chronic autoimmune systemic disorder characterized by inflammatory
responses mainly affecting the synovial joints. Interleukin-23 (IL-23) is a heterodimeric pro-inflammatory
cytokine secreted by activated dendritic cells and activated macrophages. IL-23 is the key cytokine
controlling inflammation in peripheral tissues leading to the development of autoimmune diseases. The
objective of our study was to determine the relationship between the IL-23 level and disease activity in RA
patients. Sixty RA patients were included in the study with mean age of 40 years; they included 44 (73.3 %)
females and 16 males (26.7 %). The clinical parameters of disease activity were determined, including the 28-
joint disease activity score (DAS28), serum levels of C-reactive protein (CRP), Anti-citrullinated peptide
antibody (ACPA), rheumatoid factor (RF), and TNF-α and the degree of bony erosions based on X-rays.
Patients were subdivided into active disease group (n=30) with DAS28 score higher than 5.1 (Group I); and
remission group (n=30) with DAS28 score less than 2.6 (Group II). Thirty healthy individuals in the same age
group of RA patients including 22 (73.3%) females and 8 males (26.7%) were randomly selected as the
control group (Group III). The levels of IL-23 were determined by enzyme-linked immunosorbent assay
(ELISA) and the correlations between the serum levels of IL-23 and disease activity parameters of patients
with RA were determined. Serum levels of IL-23 were significantly higher in RA patients during active stage
of the disease in comparison to the patients in remission and the control group. There was a significant
positive correlation between serum IL-23 levels in RA patients and individual disease activity parameters. It
is concluded that elevated serum IL-23 level may be a useful marker to detect active RA and disease
progression in patients with RA.