Requirement of immunoglobulin Fc portion in LDV-enhanced antibody-mediated thrombocytopenia. Groups of 4 BALB/c mice received either 3 μg control or anti-mouse platelet (anti-plt) rabbit polyclonal IgG or 6 μg anti-mouse platelet rabbit polyclonal F(ab′)2 1 day after LDV infection or administration of saline. Platelets were counted 2 days after antibody administration. ○ represents each individual datum; •, means ± SEM.