It is well known that cancer patients have specific and nonspecific immunosuppressive substances in their sera that depress cellular immunity. Plasma exchanges have been attempted to remove these immunosuppressive factors and improve the immunity to cancer. Double infiltration plasmapheresis has also been attempted and has been found to remove the immunosuppressive substances efficiently without a large volume substitution. Using these methods, an improvement in performance status and clinical symptoms and reduction of tumor size have been observed. Cancer chemotherapy has several severe side effects. Double filtration plasmapheresis is also clinically applied as a surplus carcinostatic drug adsorption method to alleviate systemic adverse reactions.
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.
For the purpose of activating the immune system in the living body, we made use of pokeweed mitogen (PWM). PWM, a type of lectin, has the potential to induce anticancer cells. In order to utilize this potential and apply it to cancer therapy by hemoperfusion with PWM, the lectin is immobilized on the surface of synthetic polymer beads and these beads are packed into a minicolumn. Human peripheral lymphocytes were activated by circulatory contact stimulation through the PWM column for 1h. After circulatory contact stimulation through the column, lymphocytes were collected and used as effector cells. Cytotoxicity tests were measured by 51Cr-release assay using K-562 cells and Daudi cells for targets. This material could enhance natural killer activity and induce cytotoxicity against natural-killer-resistant Daudi cells. Lymphocytes activated by the PWM column were injected intraregionally into nude mice bearing MKN-1 tumor, and suppression of tumor growth was recognized. Anticancer activities by direct hemoperfusion treatment with a PWM minicolumn were examined in Vx2-tumor-bearing rabbits. A single treatment using the PWM column was performed 6 days after tumor inoculation. Suppression of the tumor growth was observable for 25 days. PWM minicolumns are a likely anticancer material, acting as immunomodulators.
Anion exchange resin fiber (Ionex) was used as a heparin adsorbent. Ionex has the adsorption capacity of 70 mglg (weight by desiccation) for heparin, and was used in an attempt to remove the heparin from blood-perfused artificial organs, before the blood was transfused back into the patients. In the ex vivo study, the 5 systemically heparinized dogs (500 U/kg) were treated with a 3540 g column of Ionex, by direct hemoperfusion (DHP). The concentration of heparin was significantly reduced, within 15 to 60 minutes, using the Ionex. This suggested the possibility of removing excess heparin from the living body. In in vitro, the relationship between the amount of
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