Effects of Vitamin D3 level on the gene expression of Immune checkpoint Cytotoxic T-lymphocytes antigen-4 in Iraqi patients with rheumatoid arthritis

Background: Rheumatoid arthritis is chronic autoimmune inflammatory disease that affects synovium, rheumatoid arthritis. Antigen presentation cells (APCs) link B7-1 and B7-2 with cytotoxic T-lymphocyte related protein-4 (CTLA-4), the member of the immunoglobulin superfamily, that causes T-regulatory cells to cause APCs to produce an inhibitory signal to autoreactive T cells (Treg). This study looked at the effects of vitamin D3(Vit-D3) on the expression of the CTLA-4 gene in whole blood taken from RA patients.Methods: The case control study was conducted on 100RA patients acute and remission stages of the disease depending on DAS-28 and CDAI with respect to the level of vitamin D3. The cases and samples were obtained from Baghdad Teaching Hospital, Baghdad, Iraq from Jun 2022 to January 2023. In addition,45 healthy subjects were enrolled in this study. Standardized gene expression at a level of a reference gene (GAPDH) and enumerated by the ∆Ct-value and fold change (2-∆∆Ct) method using qPCR. The ESR was measured in all subjects and serum CTLA-4, anti-cyclic citrullinated peptide (ACCP), RF was measured using ELISA techniques. The D3 level was assessed using immunofluorescent technique.Results: Significantly increased ESR and serum CTLA-4 levels, ACCP, CRP, RF in RA patients compared to controls (p≤0.05), respectively. The vitamin D3 was significantly reduced in acute cases and substantial raised in remission case compared to the controls (p≤0.05) fold change of gene expression was dramatically elevated in patients excepts in acute male cases compared to 1. There was a significant positive correlation between vitamin D3 and CTLA-4 expression.Conclusion: The current study showed that Vit-D3 up-regulates CTLA-4 gene expression as the defensive mechanism in contradiction of a severity of a disease and possible therapeutic targets through the action of Treg population and immunotolerance