The in vivo behaviour of chromium-labelled platelets was studied in normal, C6 deficient and C3-9 depleted rabbits following the injection of a potentially lethal dose of an endotoxin (S. marcescens). The majority of labelled platelets were acutely destroyed in normal rabbits and only a small proportion returned briefly to the circulation. All normal rabbits subsequently died. In marked contrast, labelled platelets survived normally in C3-9 depleted rabbits following injection of the endotoxin and no C3-9 depleted rabbit died. In C6 deficient rabbits, platelets were acutely sequestered but destroyed to only a variable degree. C6 deficient rabbits, in which platelet recovery following early sequestration was greater than 65%, survived subsequently, whereas C6 deficient rabbits, in which platelet recovery was less than 45%, died. Platelet factor 3 (PF3) activation by endotoxin was also studied both in vivo and in platelet rich plasma in vitro. A major degree of PF3 activation occurred in normal rabbits, a minor degree in C6 deficient rabbits and none in C3-9 depleted rabbits. A direct association was found between complement status, PF3 activation, platelet survival and subsequent mortality following endotoxin injection.
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Brown et al. (2009) studied this question.