(A) Cold storage leads to Intracellular calcium leakage in platelets, resulting in shape change and activation of GPIIb/IIIa receptor through calcium inside-out signalling. Fibrinogen (complexed with FXIII on γ chain) in stored autologous plasma binds to GPIIb/IIIa (B) Upon activation, thrombin cleaves fibrinopeptides to convert fibrinogen monomer to fibrin, as well as FXIIIB to activate FXIIIA. Platelets act as nucleation site for fibrin polymerization, and FXIIIA mediates γ–dimer (longitudinal and transverse), γ-tetramer, α-polymer, αγ-hybrid crosslinks (covalent bonds) in laterally aggregated fibrin polymer (soft clot) to form a strong clot (hard clot) with thinner fibres. D, fibrinopeptide D; E, fibrinopeptide E; GP, glycoprotein.