Immunohistological Studies of Coagulation Factors in Normal Blood Vessels and Platelets
Rabbit antisera to factors II, V, VIII (related protein), X, XI, fibrinogen and fragment D have been used to localise these factors in normal blood vessels and platelets by an indirect fluorescent antiglobulin technique. Localisation of factors V and VIII (RP) confined, to the endothelium of normal blood vessels was confirmed but the presence of fibrinogen and fragment D at this site was variable and these latter antigens were also demonstrated in the sub-intima and media. There was no evidence for the presence of prothrombin and factor X in normal blood vessels. Platelets, separated by albumingradient centrifugation were washed up to 12 times in buffer with and without Ca++. Factor VIII (RP) and factor V were present in platelets and resisted removal by repeated washings. Initial studies indicated that factor XI is not present in platelets or is easily removed. Weakly positive reactions were obtained for prothrombin with four-times washed platelets but the reaction was enhanced by repeated washings. Factor X (or Xa) was removed from platelets by Ca-free buffer but not by Ca - containing buffer. The results indicate the selective presence of coagulation factors in vascular endothelial cells and platelets and are consistent with the finding of a Ca-dependent link between phospholipid and factor Xa which was also demonstrated in conventional chromatographic studies.