Immunogold labeling of megakaryocytes.
Immunogold labeling of megakaryocytes with anti-αIIbβ3 antibody (A, B) and antifibrinogen antibody (C-G). In both cases, binding of antibodies was revealed with a goat anti-rabbit IgG adsorbed onto 10-nm gold particles. The cryosections embedded in a thin film of methylcellulose were observed with a JEOL JEM-1010 transmission electron microscope at 80 kV. In A, a normal megakaryocyte shows abundant labeling for αIIbβ3 on the plasma membrane and in the DMS (arrowheads). Occasional beads were seen on the membranes of α-granules (inset). In B, little or no staining for αIIbβ3 was seen on the membranes of the megakaryocytes from an αIIb-deficient mouse. In the megakaryocyte of a normal mouse (C), fibrinogen (arrowheads) is essentially present in the α-granules (g), as also illustrated at higher magnification (E, F). No labeling was found in the α-granules (g) of αIIb-deficient mice (D, G), though some labeling was present in externally accessible dilated channels. (A-D) Bars = 0.5 μm; (E-G) Bars = 0.1 μm.
