Theoretical background of effect mechanism by extracorporeal immunomodulation.

Therapeutic plasmapheresis has usually been applied to diseases with unknown causes. Clear analysis of the mechanism of the effect that apheresis has on diseases derived from unknown causes has not been completed. The effect of leukocytapheresis on ulcerative colitis (UC) or rheumatoid arthritis (RA) also lacks clear analysis, but removal of 10(10) adhesive cells resulted in the suppression of both acute and chronic inflammatory reactions. The number of cells removed was not unreasonable for efficacy. A quite acceptable explanation is that the cells activated in the inflammatory lesions are more adhesive than nonactivated cells. However, only a few minutes of contact with the surface of the device can activate blood immune cells. All of the apheresis therapies, not only leukocytapheresis, should be evaluated for their efficacies, excluding the effects of contact activation. According to results presently available, the suppressive effect of leukocytapheresis on RA or UC is through to depend upon the removal of activated inflammation related cells that might transfer inflammatory signals. It may be that those cells removed are bound because of cell stimulation caused by microorganisms or foreign bodies.