The association between CD28 expression on CD4⁺ and CD8⁺ T cells and disease activity in systemic lupus erythematosus patients
CD28, a key T-cell co-stimulatory molecule, is implicated in immune dysregulation in SLE patients and may serve as a biomarker for disease activity. This research pointed to evaluate relations between CD4 + CD28 + and CD8 + CD28 + T-cell percentages and SLE activity (SLEDAI-2 K), clinical/laboratory markers. This cross-sectional study involved 100 people (34 controls, 66 SLE patients diagnosed according to the 2019 EULAR/ACR criteria for SLE and stratified by SLEDAI-2 K into a group with mild activity [n = 33] and a group with high activity [n = 33]). Flow cytometry quantified CD28 expression on CD4 + /CD8 + T-cells. High-activity SLE featured more hypertension (36.4% vs 21.2% in low-activity patients), renal issues (proteinuria 66.7%, hematuria 48.5%, casts 42.4%; all P < 0.001), pancytopenia, higher ESR/anti-dsDNA, and lower C3/C4. CD4 + CD28 + T-cells declined stepwise from controls (CD4 + CD28: 12.7 ± 3.8%) to (8.1 ± 3.1%) in low-activity SLE patients to (4.6 ± 3.2%) in high-activity SLE patients. On the other hand CD8 + CD28 + T-cells in controls (9.1 ± 3.8%) were then mildly elevated to (11.2 ± 5.5%) in low-activity SLE patients and then declined again to (4.1 ± 2.8%) in high-activity SLE patients (all P < 0.001). These showed strong inverse correlations with the SLEDAI-2 K score (r = − 0.564 for CD4 + CD28 and r = − 0.685 for CD8 + CD28, all p values < 0.001). They remained independently associated in multivariate regression analysis (B = − 0.83 and − 0.84, respectively; both P < 0.001), even after adjustment for age and disease duration. The expression percentages of CD28 on CD4 + and CD8 + T-cells is strongly linked with disease activity and clinical manifestations in SLE patients. So the study indicates that CD28 may serve as a potential biomarker for disease activity in SLE patients.