title: Immunocytochemical localization of fibrinogen, platelet factor 4, and beta thromboglobulin in thin frozen sections of human blood platelets.
abstract: Affinity-purified monospecific antibodies against human fibrinogen and the platelet-specific proteins platelet factor 4 and beta thromboglobulin were used to localize these antigens in thin and ultra-thin frozen sections of mildly fixed, washed human blood platelets. By immunofluorescent double-labeling experiments the distribution of fibrinogen was compared to that of platelet factor 4 and beta thromboglobulin. All three antigens occurred in virtually all platelets and showed and identical, dotlike distribution. For immunoelectron microscopy we used protein A-colloidal gold on ultra-thin frozen sections to visualize the specific reaction indirectly. The staining for platelet factor 4, beta thromboglobulin, and fibrinogen localized exclusively over alpha-granules of washed platelets. Within the granules, platelet factor 4 was localized preferentially in the electron dense, alpha-granule nucleoid, whereas fibrinogen was more predominant in the electron-lucent granule periphery. Beta thromboglobulin localization did not show a preferential intragranular distribution.
mesh_terms: D000941:Antigens / Q000032:analysis; D001609:Beta-Globulins / Q000032:analysis*; D001792:Blood Platelets / Q000032:analysis / Q000648:ultrastructure*; D005293:Ferritins; D005340:Fibrinogen / Q000032:analysis* / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006046:Gold / Q000378:metabolism; D006651:Histocytochemistry; D006801:Humans; D008854:Microscopy, Electron; D010978:Platelet Factor 4 / Q000032:analysis* / Q000276:immunology; D001620:beta-Thromboglobulin / Q000032:analysis* / Q000276:immunology
chemical_list: D000941:Antigens; D001609:Beta-Globulins; D001620:beta-Thromboglobulin; C018943:ferritin-protein conjugates; D010978:Platelet Factor 4; D006046:Gold; D005340:Fibrinogen; D005293:Ferritins