HMGB1 and COVID-19: Moreover, the expression levels of inflammatory factors including tumor necrosis factor alpha (TNF‐α), interleukin‐1β (IL‐1β) and interleukin‐6 (IL‐6) were all upregulated in acute and post‐acute COVID‐19, though other cytokines like interleukin‐10 (IL‐10) and interleukin‐18 (IL‐18), as well as neuroinflammation‐related proteins like high mobility group box 1 (HMGB1) and plasminogen activator inhibitor‐1 (PAI1) remained nearly unchanged (Figure 2k).