<prompt> Answer this question truthfullyWhat is the cause of febrile non-hemolytic transfusion reaction and when does it typically occur?  <response>: <reason> What is the cause of febrile non-hemolytic transfusion reaction and when does it typically occur? Febrile non-hemolytic transfusion reaction is typically caused by cytokine release from residual plasmaleukocyte debris and occurs immediately after transfusion. 