Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 134

The filter material may be modified to alter the surface charge and improve the effectiveness. The mechanism of leukocyte removal by the filters currently in use is probably a combination of physical or barrier retention and also biological processes involving cell adhesion to the filter material.

Because leukocytes are contained in red cell and platelet components, filters have been developed for both of these components. Filters are available as part of multiple‐bag systems, including additive solutions, so that leukocytes can be removed soon after collection and the unit of WB converted into the usual components. Filtration removes 99.9% of the leukocytes, along with a loss of 15–23% of the red cells [53]. Thus, bedside leukodepletion is not used. Filters fail to achieve the desired leukodepletion from 0.3 to 2.7% of units. Red cell components from donors with sickle cell trait often occlude white cell reduction filters.

It appears that febrile nonhemolytic transfusion reactions are caused not only by leukocyte antigen–antibody reactions but also by the cytokines produced by leukocytes in the transfused blood component (see Chapter 16). This would be more effectively prevented if the leukocytes were removed immediately after the blood was collected, avoiding the formation of cytokines. This is referred to as “prestorage” leukodepletion. Filtering the red cells at the bedside at the time of transfusion has the advantage of not requiring a separate blood bank inventory, but the disadvantage of allowing cytokines to accumulate during blood storage, thus being less effective in preventing febrile transfusion reactions (see Chapter 16). Also, bedside filtration is not as effective in removing leukocytes as filtration in the laboratory under standardized conditions and with a good quality‐control program [53]. Because the leukocyte content of the depleted units is very low, the usual methods for leukocyte counting are not accurate [53–55]. The Nageotte chamber and flow cytometry are used for this quality‐control testing [53, 55].

Table 5.8 Established or potential adverse effects of leukocytes in blood components.

Immunologic effects	Alloimmunization
Febrile nonhemolytic transfusion reactions
Refractoriness to platelet transfusion
Rejection of transplanted organs
Graft‐versus‐host disease
Transfusion‐related acute lung injury
Immunomodulation	Increased bacterial infections
Increased recurrence of malignancy
Infectious disease transmission	Cytomegalovirus infection
HTLV‐I infection
Epstein–Barr virus infection

HTLV‐I, human T‐lymphotropic virus I.