Intracytoplasmic Expression of IL-6 and IL-17A in Circulating CD4+ T Cells Are Strongly Associated with and Predict Disease Activity in Rheumatoid Arthritis: A Case-Control Study in Ghana

Abstract

Background . T cell cytokines play important roles in the development and progression of rheumatoid arthritis (RA). Loss of Th1/Th2 and Th17/Treg balance has been reported in several inflammatory autoimmune diseases. However, their role in RA within hitherto rare Ghanaian context has not been explored. Here, we evaluated the intracytoplasmic CD4+ T cell cytokine patterns in rheumatoid arthritis patients in Ghana and determined their relationship with disease activity. Methods . This case-control study included 48 newly diagnosed RA patients and 30 apparent healthy controls from two major hospitals in Ghana. Validated structured questionnaires were administered to obtain demographic data; blood samples were collected and processed for flow cytometric analysis. Results . IFN- γ , TNF- α , IL-4, IL-6, IL-10, IL-17A, IL-6/IL-4, and IL-17/IL-10 expressions were significantly higher in RA cases compared to the healthy controls. The expression of IL-6 (0.00 (0.00-0.98) vs. 0.82 (0.34-1.10) vs. 1.56 (1.39-1.68), <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>p</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.0001</mml:mn></mml:math>), IL-17A (0.00 (0.00-0.02) vs. 0.19 (0.09-0.30) vs. 0.99 (0.64-1.25), <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>p</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.0001</mml:mn></mml:math>), and IL-17A/IL-10 (0.00 (0.00-0.39) vs. 0.15 (0.09-0.26) vs. 0.88 (0.41-1.47), <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mi>p</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.0001</mml:mn></mml:math>) increased significantly from the healthy controls through RA patients with low DAS scores to RA patients with moderate DAS scores. IL-6 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>β</mml:mi><mml:mo>=</mml:mo><mml:mn>0.681</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:msup><mml:mrow><mml:mi>r</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>=</mml:mo><mml:mn>0.527</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mi>p</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.0001</mml:mn></mml:math>), IL-17A (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M7"><mml:mi>β</mml:mi><mml:mo>=</mml:mo><mml:mn>0.770</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M8"><mml:msup><mml:mrow><mml:mi>r</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>=</mml:mo><mml:mn>0.593</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M9"><mml:mi>p</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.0001</mml:mn></mml:math>), and IL-17A/IL-10 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M10"><mml:mi>β</mml:mi><mml:mo>=</mml:mo><mml:mn>0.677</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M11"><mml:msup><mml:mrow><mml:mi>r</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>=</mml:mo><mml:mn>0.452</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M12"><mml:mi>p</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.0001</mml:mn></mml:math>) expressions were significantly directly associated with DAS28 scores. IL-6 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M13"><mml:mtext>cutoff</mml:mtext><mml:mo>=</mml:mo><mml:mn>1.32</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M14"><mml:mtext>sensitivity</mml:mtext><mml:mo>=</mml:mo><mml:mn>100.0</mml:mn><mml:mi>%</mml:mi></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M15"><mml:mtext>specificity</mml:mtext><mml:mo>=</mml:mo><mml:mn>100.0</mml:mn><mml:mi>%</mml:mi></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M16"><mml:mtext>accuracy</mml:mtext><mml:mo>=</mml:mo><mml:mn>100.0</mml:mn><mml:mi>%</mml:mi></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M17"><mml:mtext>AUC</mml:mtext><mml:mo>=</mml:mo><mml:mn>1.000</mml:mn></mml:math>) and IL-17A (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M18"><mml:mtext>cutoff</mml:mtext><mml:mo>=</mml:mo><mml:mn>0.58</mml:mn></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M19"><mml:mtext>sensitivity</mml:mtext><mml:mo>=</mml:mo><mml:mn>100.0</mml:mn><mml:mi>%</mml:mi></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M20"><mml:mtext>specificity</mml:mtext><mml:mo>=</mml:mo><mml:mn>100.0</mml:mn><mml:mi>%</mml:mi></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M21"><mml:mtext>accuracy</mml:mtext><mml:mo>=</mml:mo><mml:mn>100.0</mml:mn><mml:mi>%</mml:mi></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M22"><mml:mtext>AUC</mml:mtext><mml:mo>=</mml:mo><mml:mn>1.000</mml:mn></mml:math>) presented with the best discriminatory power in predicting moderate DAS scores from low DAS scores. Conclusion . Th1- and Th17-related cytokines predominate in the pathophysiology of RA, with IL-6 and IL-17 being principally and differentially expressed based on the severity of the disease. IL-6 and IL-17A could serve as useful prognostic and disease-monitoring markers in RA in the African context.