Then antibodies are required for this reaction to take place. If these were anaphylaxis reactions, the how must be answered. An infection taken systemic (which would be the case during dialysis) could double for systemic shock, with the root cause being an infection. maybe, maybe not, but for antibodies to be present to cause this shock, an antigen must have been introduced in the patients that had this reaction. A similiar antibody producing antigen would need to be introduced into the patients in order for an antiphlxsis reaction to occur. How did that happen?