The localization of factor V within normal human platelets and the demonstration of a platelet-factor V antigen in congenital factor V deficiency.
Separation of human platelets from plasma by a modified gel-filtration technique reveals very low levels of factor-V activity of the platelet suspension. Repeated freezing and thawing increases the factor-V activity in various factor-V assays. This activity neutralized the inactivating effect of a rabbit-antihuman factor V antibody to plasma factor V, while intact platelets had almost no such capacity. Washed and normal platelets and gel filtered platelets showed marked positive fluorescence after treatment with antifactor V serum and FITC labelled sheep antirabbit immunoglobulin. Fluorescence was inhibited by previous incubation of the antifactor V serum and platelet lysates. Platelets of a factor V deficient patient showed the same fluorescence pattern as normal platelets indicating that they contained a factor V antigen. These platelets showed after lysis no effect in various factor V assays. From these studies it is concluded that the localization of factor V is within the platelets.
D000941:Antigens / Q000032:analysis*; D001792:Blood Platelets / Q000032:analysis* / Q000276:immunology; D002469:Cell Separation; D002498:Centrifugation; D002850:Chromatography, Gel; D005165:Factor V / Q000032:analysis* / Q000276:immunology; D005166:Factor V Deficiency / Q000097:blood / Q000276:immunology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D009500:Neutralization Tests
D000941:Antigens; D005165:Factor V