Complement levels can fall to very low levels within a few hours due to the development of immune complexes so that the fall in complement here may be a reflection of activation; consumption of complement in response to the physiological stress response and reduction of complement levels have been reported in acute pancreatitis with the levels of C3 and C4 being sensitive and accurate to the severity of the pancreatitis [45], whilst a fall in C3 and its reversibility was predictive in renal allograft rejection and recovery [46]. Here, C4A is linked to acute pancreatitis.