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. 2020 Jul 28;190(4):520–524. doi: 10.1111/bjh.16938

Fig 2.

Fig 2

Schematic illustration of the contact, complement and renin–angiotensin systems. Green arrows represent activating functions and red stop rods represent inhibitory functions. Only selected reactions are represented, relevant to the discussion. Contact system: FXII, FXI: Factors XII and XI; PK, prekallikrein; PKa, activated kallikrein; HK, high‐molecular weight kininogen; B2R, bradykinin receptor B2; BK, bradykinin; BK1‐5, bradykinin 1‐5; PLG, plasminogen; PLM, plasmin; tPA, tissue‐type plasminogen activator. Renin–angiotensin system: ACE, angiotensin‐converting enzyme; ACE2, angiotensin‐converting enzyme 2; AngI, angiotensin I; AngII, angiotensin II; Ang1‐7, angiotensin 1‐7; AT1R, angiotensin type 1 receptor; MAS‐R, MAS receptor. Complement system: MBL, mannose‐binding lectin; MASP1/2, mannan‐binding lectin‐associated serine protease‐1/2. Other factors and components of the three systems are shown with conventional designations. SARS‐CoV and SARS‐CoV‐2 predicted proteins are shown as red‐filled rectangles. Also represented is the negative regulation of cell‐surface ACE2 through internalisation upon interaction and entry of the CoV‐1 and CoV‐2 spike proteins.