Threshold model of TRALI: On the y-axis the recipient's threshold for developing TRALI is lowered in the presence of shock, chronic alcohol abuse, intravascular volume overload, higher peak airway pressure while being mechanically ventilated, and current smoker. On the x-axis are the blood product factors (volume of high titer cognate HLA class II antibody or sufficient volume of high-titer HNA antibody), which are cumulative and together may trigger TRALI in the recipient if above the recipient threshold.