Apheresis techniques and cellular immunomodulation.

Abstract

Significant advances have been made in the capabilities to remove white blood cells (WBCs) from blood by both centrifugal and filtration techniques. New techniques have applications for both donor products (and their effects upon the recipients) and for selected disease therapeutics. The immunomodulatory effects of donor WBCs may be therapeutic, e.g., granulocytes harvested by apheresis may be used for the treatment of sepsis, or mononuclear cells collected by apheresis for peripheral blood progenitor (stem) cell transplantation or graft versus leukemia effect. In contrast, WBCs are removed from many transfusable components to decrease the immune effects in recipients. This has been accomplished primarily by the use of leukoreduction filters although newer adaptations of centrifugal equipment allow for the reduction of WBCs to target range of <1 x 10(6) WBCs/product. Therapeutic WBC removal by centrifuge has been used for treatment of the effects due to elevated levels of WBCs or platelets. More specific cellular immunotherapy has included lymphocytapheresis for the treatment of autoimmune diseases such as systemic lupus erythematosis (SLE). Various mononuclear cell fractions collected by apheresis have been used for lymphokine activated killer cells (LAK) and tumor infiltrating lymphocytes (TIL) cell therapy or autologous stem cell transplantation. The development of WBC adsorbent filters for therapeutic use has evolved as nonspecific filter materials have been demonstrated to show selective WBC removal, and filter columns permit therapeutic reductions in WBCs using online filtration therapy. Specific adsorption techniques, e.g., CD-34 selection, are in use in vitro and indicate directions for further developments in cellular immunotherapy.