Increased CFU-Mk in thrombocytopenic individuals.

Megakaryocyte colonies were grown on collagen matrix as described in “Materials and methods.” Cells were fixed and stained for GpIIb/IIIa expression. On the left, double-chamber slides are shown (1 ×, unmagnified) for 1 unaffected (IV-8) and 1 thrombocytopenic individual (IV-10). Dark spots (pink or red) represent individual megakaryocyte colonies; only the larger colonies are visible without magnification. In the center panels, representative megakaryocyte colonies are shown under low-power magnification (40 ×). On the right, higher power views of megakaryocytes (200 ×) demonstrate the presence of proplatelet processes and platelet fragmentation in unaffected and thrombocytopenic samples. Similar data were obtained for a second thrombocytopenic individual (V-14).