PF4 and infection: Several lines of evidence now attest that autoantibodies against PF4 may arise under a large number of specific conditions, with several additional risk factors or associations, including disease, infection, and surgery, and as noted by a wide variety of researchers [3,16,20,23,30,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53].