The requirement for platelets in the active Arthus reaction

The active Arthus reaction was completely inhibited in rabbits made thrombocytopenic with platelet antiserum. Platelets or some platelet factor is necessary for the development of immune vasculitis in this model. Since the classic Arthus reaction depends on the union of extravascular antigen with intravascular antibody, it is probable that the missing platelet factor is an agent that alters vascular permeability.