In apheresis, a tube system is used to guide a patient’s blood into a centrifuge, where gravity causes the individual blood components of the plasma to separate into different layers. In this way, leukocytes can be “washed” from the patient’s blood in a targeted manner during leukocyte apheresis, for example. This procedure is relevant in the context of autoimmune diseases, for example.
What is leukocyte apheresis?
The therapeutic procedure of apheresis is colloquially referred to as blood washing. In leukocyte apheresis, for example, leukocytes can be specifically “washed” from the patient’s blood. The therapeutic procedure of apheresis is colloquially referred to as blood washing. In this process, the blood is purified of excess components. The procedure takes place extracorporeally and thus outside the patient’s body, in that the pathogenic substances are removed via a catheter in a similar way to dialysis. The pathogenic substances may be proteins, protein-bound substances or whole cells present in the blood plasma. The patient receives the purified blood back after the cleanup. Leukocyte apheresis is a subtype of apheresis that involves cleansing the plasma of leukocytes. These are white blood cells that are sometimes involved in the body’s defense against pathogens or other foreign structures. Leukocytes are thus a part of the immune system. Apheresis of the immune cells is particularly necessary if the cells are present in an unusually high concentration and are harming the patient. This may be the case, for example, in the context of autoimmunologic reactions.
Function, effect, and targets
Leukocyte apheresis take place for the treatment of various autoimmune diseases. For example, the therapeutic procedure can be used in the context of multiple sclerosis and has already been established as a therapy for acute relapses, especially in patients with abnormal reactions to cortisone. Autoimmunological processes are directed against the body’s own tissue and cause inflammation in this tissue. In leukocyte apheresis, excess leukocytes are removed from the patient’s blood plasma to combat autoimmunological inflammation, for example. Therapeutic apheresis has already established itself in various forms. In addition to unselective for complete plasma substitution, selective plasmapheresis exists, in which filtration or adsorption separates pathogenic and supernumerary substances from the plasma and returns the purified plasma to the patient’s body. Leukocyte apheresis is thus equivalent to selective apheresis. In the apheresis procedure, the donor’s blood is drawn from a vein, such as the leg or neck vein, using a catheter. A closed sterile tube system is connected to the catheter, which can only be used once each. The blood flows into the tube system where it is interspersed with a small amount of anticoagulant solution to prevent blood clotting within the system. Mixture of blood and anticoagulant travels through the tubing system into a centrifuge that creates an artificial gravity field. The blood components separate into individual layers in this field depending on their density. In this way, the leukocytes can be collected. All other blood components are returned to the patient via the closed tube system. The apheresis procedure can take up to two hours. Apheresis procedures are performed exclusively on an inpatient basis and require regular monitoring of plasma, as other blood components may be washed out during apheresis and need to be replaced.
Risks, side effects, and hazards
In most cases, apheresis procedures are of little concern to the patient. Sometimes the most common side effects are reactions to the anticoagulant administered, such as a metallic taste in the mouth and a tingling sensation in the lips or extremities. Nausea occurs only in rare cases. A cold sensation is also conceivable during the procedure. Patients with poor circulation are advised after leukocyte apheresis not to sit up too rashly or even to stand up hastily. The patient’s circulation should recover for at least five minutes after apheresis. Only in extreme cases do fainting spells occur after apheresis.An extreme case also occurs if the anticoagulant is not sufficiently broken down by the patient’s liver. In such a case, leukocyte apheresis can permanently restrict blood clotting. In such cases, there is a temporary tendency to bleed and clotting must be restored to normal with donor blood. This is also the case if too many physiologically necessary substances have been removed from the blood together with the leukocytes. Since leukocytes fulfill an immunological function, there must still be enough leukocytes in the blood after apheresis to protect the patient from pathogens. Leukocytes are constantly being replenished. Normally, therefore, patients are not affected by a permanent impairment of the immune system. During therapy, however, they are usually more susceptible to infections. If, for unknown reasons, leukocytes are not replenished in sufficient quantities, substitution by donation is also necessary in this context. A special feature of leukocyte apheresis is its applicability in the context of leukocyte donations. Thus, a certain amount of donor substance can be removed from a healthy person by means of the procedure. Unlike whole blood donation, apheresis can obtain the blood components to be donated individually and in high purity. Apheresis procedures are therefore also relevant in the context of donors and are considered the only procedures to be able to obtain certain blood components from a donor in sufficient quantities. In this context, modern cancer therapy, for example, benefits from apheresis techniques. In the context of modern cancer therapy, apheresis techniques enable, for example, the transplantation of blood stem cell preparations.
