Survival of rabbit platelets exposed to immune complexes

Rabbits injected with human serum albumin (HSA) formed detectable immune complexes after 5 days; complex formation was maximal between 11 and 14 days after which the complexes were cleared from the circulation. Platelets from control rabbits or HSA-injected rabbits had a reduced survival upon injection into rabbits in which complexes were forming. Platelets from HSA-animals tended to survive for a longer period upon injection into control rabbits than when they were injected into HSA-rabbits, raising the possibility that some of the immune complexes may have eluted from their surface. Platelets prepared from either control animals or from HSA-treated animals at the time when complexes were being cleared from the circulation (14-21 days) did not have a shortened life span in HSA- or control rabbits. When platelet survival was reduced, it could not be attributed to platelet accumulation at sites of vessel wall injury or to accumulation in kidneys damaged by immune complexes, since the tissues (aorta and kidney) appeared to be morphologically normal and free of thrombi. The reduction in platelet survival likely results from the interactions of immune complexes with the surface of platelets leading to the platelets being recognized as "foreign" and cleared from the circulation by the reticuloendothelial system.