CD81 and systemic lupus erythematosus: CD81 levels were significantly higher in SLE exosomes (n = 9) than HC exosomes (n = 6) (median (IQR), μL: 40.80 × 107 (6.01 × 107–44.00 × 107) vs. 5.30 × 107 (4.14 × 107–7.68 × 107), respectively; p = 0.008) (Fig. 1c).