Relationship between serum levels of T Cell Immunoglobulin and Mucin-Domain Containing Molecule-3 and Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by autoantibody production, immune complex deposition, and cytokine activation. T-cell immunoglobulin and mucin domain-containing molecule-3 (Tim-3) has a role in many chronic autoimmune diseases by regulating T cell immune responses and Th17/ Treg balance. Tim-3 was found to be elevated in the sera of patients with autoimmune diseases such as SLE. We aimed to quantify the serum levels of Tim-3 in patients with SLE and healthy controls and to investigate the relationship between their serum levels and the disease activity. This case-control study was conducted on 85 subjects: 25 participants age and sex-matched apparently healthy controls (group 1), 30 patients with SLE with disease activity (group 2), and 30 patients with SLE without disease activity (group 3). Group 2 was further subdivided into mild, moderate, and severe flare groups according to disease severity. Serum levels of Tim-3 in all groups were measured by ELISA. 2019 EULAR/ACR Classification Criteria for SLE was used to diagnose patients with SLE and SELENA SLEDAI was used to assess the disease activity. There was a highly significant increase in serum levels of Tim-3 in patient group as compared with controls (p < 0.001). Also, there was a highly significant increase in serum levels of Tim-3 in group 2 when compared with group 3 and group 1 (p < 0.001). There was a negative correlation between serum levels of Tim-3 and WBCs count (r=-0.473, p=0.000), platelets count (r=-0.437, p= 0.000), serum C3 levels (r=-0.503, p=0.000) and serum C4 levels (r=-0.342, p=0.000). Also, there was a positive correlation between serum levels of Tim-3 and 24-hour urine protein (r=0.557, p=0.000), presence of RBCs in urine (0.477, p=0.000), presence of pus in urine (r=0.410, p=0.001), ESR (r=0.394, p=0.002) and SELENA SLEDAI score (r=0.643, p=0.000). The area under the ROC curve (AUC) values indicated that the serum levels of Tim-3 was significantly discriminative of SLE patients from healthy controls, AUC for serum Tim-3 was 0.768 (at a cut-off value >1.28 ng/mL, sensitivity was 80.00%, and specificity was 76.00%). Serum levels of Tim-3 were elevated in patients with SLE and was associated with the disease activity. These results suggested that serum Tim3 may represent prospective biomarkers for the diagnosis of SLE and its activity. This highlights the need for future research to identify how this association contributes to the development of SLE.