Abstract: A method for extracorporeal treatment of a body fluid of a patient suffering from sepsis, in an extracorporeal flow line, comprising removing at least one harmful substance from the body fluid of the patient. In a first injection step, a first mixture containing functionalized magnetic particles bound to at least a first binding agent at least directed against a first type of target molecules contained in the body fluid is added to the extracorporeal flow line comprising a sample of the body fluid extracted from a patient and containing at least the first type of target molecules. The first mixture is injected in a therapeutically effective dose necessary to reduce a concentration of the target molecules of at least the first type in the body fluid sample of the patient, followed by a mixing step and a separation step for reduction of the target molecule concentration.