A 26-year-old female was hospitalized with gingival bleeding and skin ecchymoses for 1 month. Laboratory tests: PLT 28×10<sup>9</sup>/L, Hb 120g/L, WBC 5.6×10<sup>9</sup>/L. Bone marrow smear showed 105 megakaryocytes (15 immature, 80 granular, 8 platelet-producing, 12 naked nuclei). After corticosteroid therapy, bleeding tendency resolved in 1 week, and PLT rose to 126×10<sup>9</sup>/L by 3 weeks. The LEAST likely mechanism of action is: