Suppression of megakaryocyte production by IgG from ITP plasma. Cultures contained CD34⁺ cells, rHuMGDF, and normal plasma, as described, except that purified IgG (100 μL of 1.2 mg/mL) from either ITP patients (ITP-5 or ITP-6) or control subjects was added. Total megakaryocytes were calculated as described in Figure 3. Results reflect the mean (± SD) of 6 separate cultures for each IgG. Control results were calculated as a group.