Immunolocalization of stomatin to platelets and megakaryocytes.

A blood smear was analyzed to identify stomatin in platelets by immunocytochemistry with diaminobenzidine as substrate following 30 minutes of cell extraction with TX-100 (A) and immunofluorescence microscopy following 3 minutes of TX-100 extraction (B). Immunoreactivity in the central granule membranes is intense, leaving less signal in the peripheral cytoplasm of the platelets. (C) Identification of stomatin in a megakaryocyte from bone marrow, as observed with immunofluorescence. The nucleus is free of labeling, and the cytoplasm is stained almost homogeneously, with some patches of increased cytoplasmic signal. Immunoelectron microscopy of resting platelets (D) and activated platelets (E) revealed the subcellular localization of stomatin. In resting platelets, the labeling is predominantly over the membrane of α granules (D), whereas in activated platelets, the plasma membrane is consistently labeled in addition to the granular membrane (arrows in E). Bars represent 5 μm (A and B), 10 μm (C), or 0.5 μm (D and E).