Leucodepletion filters

Leucodepletion is a technical term for the removal of leucocytes (white blood cells) from blood components using special filters.
The leucocytes present in donated blood play no therapeutic role in transfusion and may be a cause of adverse transfusion reactions.
Removal of leucocytes may therefore have a number of potential benefits for transfusion recipients.

1. Leuco -depletion Leuco-Leuco-depletion filters YANAMALA VIJAY RAJ / Mtech in clinical engineering IIT Madras/ CMC Vellore/ SCTIMST Trivandrum

2. Leucodepletion Leucodepletion is a technical term for the removal of leucocytes (white blood cells) from blood components using special filters .

3. Leucocytes Lymphocytes

4. REASON The leucocytes present in donated blood play no therapeutic role in transfusion and may be a cause of adverse transfusion reactions . Removal of leucocytes may therefore have a number of potential benefits for transfusion recipients.

5. Allo -immunization Recipient who is immunocompetent often mounts an immune response to the donor antigens, resulting in various clinical consequences, depending on the blood cells and specific antigens involved. The antigens most commonly involved are classified in the following categories: ( 1) human leukocyte antigens ( HLAs ), class I shared by platelets and leukocytes and class II present on some leukocytes; ( 2) granulocyte-specific antigens; (3 ) platelet-specific antigens (human platelet antigen [ HPA ]); (4 ) RBC-specific antigens.

6. Red cell changes during storage : John R. Hess * Professor of Pathology and Medicine, University of Maryland School of Medicine, Baltimore USA The red cell storage lesion: The storage lesion’ is the name given to all of the changes that occur to blood components during conventional blood bank storage. The red cell storage lesion includes both metabolic and physical changes.

7. P otential benefits Reduced risk of platelet refractoriness, Reduced risk of febrile non- haemolytic transfusion reactions (FNHTR ), Reduced risk of CMV transmission, Reduction in storage lesion effect, Reduction in the incidence of bacterial contamination of blood components, Possible reduced risk of transfusion-associated graft vs host disease (TA-GVHD ) Possible reduction in transfusion related immuno-modulatory (TRIM) effects, including cancer recurrence, mortality, non-transfusion transmitted infection, Possible reduced risk of transmitting variant Creutzfeldt-Jakob Disease,

8. Methods in leucodepletion Before storing After storing

9. Optimum time to remove passenger leucocytes is before storage for the following reasons : Better process control and quality assurance Lower incidence of febrile non- haemolytic transfusion reactions (FNHTR ) Lower incidence of allo-immunisation and (possibly) diminished immunomodulation that may result from the transfusion of membrane fragments Avoidance or reduction in the incidence of adverse effects directly related to the filtration process Reduction in the incidence of bacterial contamination of blood components

10. Methods of Leucodepletion Washing Freezing Buffy coat removal Micro-aggregate filtration Specific leucodepletion filters Low leucocyte apheresis devices

11. Filtration

12. Pre-storage Leuco-depletion:

13. LD filters - Structure and Design Structure : Layers of asymmetrical non-woven synthetic fibers. Mechanism : Depth filtration & absorptive mechanism. Adherence : RBCs < lymphocytes < platelets < PMNs < monocytes In platelet filters: Fibers specially coated to prevent platelets sticking.

14. WBC size vs RBC size

15. Types of Leucocyte Filters 1st Generation: Removes 90% leucocytes / Log 1 2nd Generation : Removes 99% leucocytes / Log 2 3rd Generation: Removes 99.9% Leucocytes / Log 3 4th Generation: Removes 99.999% Leucocytes / Log 4

16. Pore size and it filtrates: 170-240 micro meter : Large clot and particulate debris 40 micro meter : Micro-aggregates of fibrin, leucocytes, platelets (one log reduction) 7-10 micro meter : Micro-aggregate, cells, (three log reduction)

17. Mechanism of action of leucodepletion filters Blocking Bridging Adhesion Interception

18. EM images Reference : Asymmetric membrane filters for the removal of leukocytes from blood A . Bruil , W.G. van Aken , T. Beugeling , and J. Feijen * Department of Chemical Technology, Section of Biomaterials, University of Twente , Enschede , The Netherlands

19. Ideal scheme of pore size

20. Filter characteristics

21. Filter characteristics for leukocytes

22. Bradykinin release Bradykinin released in filtration process

23. Factors affecting filtration Number of leucocytes, Temperature (viscoelasticity ), Flow rate / Speed of filtration, Pressure, Presence of HbS , No . & function of platelets, Plasma content of cell suspension media,

24. Clogging of cells on membrane Uniform pore size Gradual decrease in pore size

25. Conclusions Polyurethane membrane filter best, Pore size distribution has considerable effect on filtration efficiency, Adhesion can be increased indirectly by reducing size of pore, Small pore size leads to clogging, Clogging can be prevented by gradual reduce in pore size, Asymmetrical filter also prevents clogging, Both adhesion and sieving mechanisms are involved in leukocyte filtration, although cell adhesion play a predominant role.