SDC1 and Arthritis: Based on H&E and immunohistochemistry staining for CD3 (T cells), CD20 (B cells), CD138 (plasma cells), and CD68 (macrophages), synovial tissue from each UA and definite arthritis group was categorized into three distinct synovial pathotypes: lympho-myeloid, diffuse-myeloid, and pauci-immune (37).