Allogeneic platelet transfusions inhibit T-cell–mediated ITP. Platelet counts in SCID mice transferred with CD19-depleted CD61 KO immune splenocytes against BALB/c (CD61⁺/H-2^d) platelets and then transfused weekly with either nothing (○; N = 5), syngeneic BALB/c platelets (▼; N = 5), or allogeneic C57BL/6 platelets (□; N = 5). Results are presented as the weekly platelet counts (×10⁹/L) after splenocyte transfer (*P < .05 for □ vs ○).