Removal of soluble biologic response modifiers (complement and chemokines) by a bedside white cell-reduction filter

Serum eye drops: a survey of international production methods

BACKGROUND

Serum eye drops (SEDs) are used to treat dry eye syndrome and non-healing corneal lesions when other treatments fail. Despite many clinical studies demonstrating the efficacy of both autologous and allogeneic SEDs, there is no internationally harmonized method for producing SEDs.

MATERIALS AND METHODS

A 40-question survey requesting information regarding donor selection, blood collection and processing, infectious disease screening, shelf life and regulatory requirements for the production of autologous and allogeneic SEDs was developed by the Biomedical Excellence for Safer Transfusion Collaborative. Survey data were collected into a database via a secure web interface and then downloaded into Excel for further analysis.

RESULTS

A total of 55 responses were received, with 21 responses from centres indicating they produce SEDs. Based on the responses, collection and processing practices differ widely, according to the size of the centre making the SEDs, and their ability to collect, process and test the blood.

CONCLUSION

Despite divergences in the methods for producing SEDs, the end result is a small-volume aliquot of serum that can be administered by a patient at home. If more centres move from producing autologous to allogeneic SEDs, this may provide an opportunity for production methods to become more standardized internationally.

Cytokines in Platelet Concentrates

There are many cytokines that have been shown to increase in platelet concentrates during storage including: proinflammatory cytokines, chemokines, and transforming growth factor β. The concentrations of these cytokines can be variable depending on the method of platelet preparation, and the leukocyte and/or platelet concentration in the product. The clinical significance of these cytokines is questionable; however, clinical data suggests that tike proinflammatory cytokines may play an important role in causing febrile non-hemolytic transfusion reactions. The clinical data to support a causative role in these reactions includes: correlational studies where high concentrations of proinflammatory cytokines were associated with a higher frequency of reactions; observational studies showing that the transfusion of platelet products with high leukocyte counts have a higher likelihood of causing reactions; and, experimental studies where products with low cytokine levels seldom cause FNHTR. The clinical relevance of chemokines and other growth factors detected in platelet concentrates remains inconclusive.

Assessment of complement activation during membrane-based plasmapheresis procedures

Previous studies have suggested that plasmapheresis procedures using a separation membrane may activate the complement system and release anaphylatoxins. This study determines the content in C3a/C3a(des Arg) and C5a/C5a(des Arg) in plasma donations obtained by the new Haemonetics Filter Core (FC) procedure and compares it to Baxter Autopheresis C (Auto-C). FC performs sequential blood centrifugation and plasma filtration on a microporous polyethersulfone membrane, while Auto-C removes blood cells by simultaneous gravitation and filtration on a rotating nylon membrane. One group of 34 donors donated on FC and two groups of 30 and 10 donors on Auto-C. Plasma aliquots were taken from the plasma units within 30 min of the end of the collection procedures, frozen at < -30 degrees C and assessed for C3a and C5a at various time points of storage. Mean C3a/C3a(des Arg) in FC plasma (N = 34) was 1,151 (range: 526-2,991), 1,092 (range: 349-3498), and 507 (range: 307-815) ng/ml at time of collection and after 6 and 12 months of storage, respectively. Respective C5a/C5a(des Arg) was 26.6 (range 4.9-74), 18.9 (9.5-42.6), and 30.9 (range: 10.7-62.3) ng/ml. Mean C3a/C3a(des Arg) was higher in Auto-C (P < 0.001): 4,724 ng/ml (N = 10; range: 2,400-7 ,360) and > 4,149 ng/ml (N = 30; 2,408- > 6,430) after 3 and 18 months storage, respectively. Mean C5a/C5a(des Arg) was 32.1 ng/ml (N = 30; range: 10.6-57.2) after 18 months of storage. Complement activation in FC plasmas appears limited compared to Auto-C, suggesting better biocompatibility of this collection device and/or a favourable impact of the sequential cell centrifugation/filtration technology used. Further studies are needed to explain differences in complement activation between apheresis procedures and to assess clinical impacts, if any.

Contamination control in nursing with filtration: part 2: emerging rationale for bedside (final) filtration of prestorage leukocyte-reduced blood products

The first part of this 2-part series focused on the manufacture of filters and the application of filtration technology to intravenous fluids and point-of-care hospital water. This second part describes an apparent emerging potential for final filtration defined as bedside filtration of blood and component blood products leukocyte-reduced at the blood center prior to storage. Final filtration serves to further reduce the leukocyte burden in a previously leukocyte-reduced blood product. Another target for final filtration includes putative soluble mediators of morbidity.Selected patients may be at greater risk for alloimmunization and refractory to the benefits afforded by transfusion of blood leukocyte reduced to the current established standards. Multiparous patients who subsequently find themselves in need of a transplanted organ are alloimmunized by exposure to fetal proteins and may be further alloimmunized by transfusion. Such effects can put them at risk for increased latency for donor organ availability and organ rejection. Kidney transplant patients find themselves the recipients of transfused blood products particularly during end-stage renal disease and recent data suggest such patients are not benefited by the levels of leukoreduction prescribed by current standards and may need more dramatic leukocyte removal. The process of blood production is described and affords a greater appreciation for the levels of white cells found in component blood products. The development of alloimmunization is reviewed and fosters greater appreciation for a discussion of the potential for therapeutic value of more dramatic leukocyte reduction and blood conditioning accomplished through the removal of soluble mediators of morbidity.

The effect of leucocyte depletion on the quality of fresh-frozen plasma

The aim of this study was to evaluate the quality of leucodepleted (LD) fresh-frozen plasma (FFP) produced using one of five whole blood filters (Baxter RS2000 & RZ2000, NPBI T2926, Macopharma LST1 and Terumo WBSP) or two plasma filters (Pall LPS1 and Baxter FGR7014). Whole blood or plasma was filtered within 8 h of collection at an ambient temperature. Samples were taken pre- and post filtration for analysis of coagulation factors and complement activation (n = 7--12 for each type of filter). All filtered units (209--286 ml) contained < 5 x 10(6) residual leucocytes and < 30 x 10(9)/l platelets. Statistically significant losses of factors V, VIII, IX, XI and XII and increases in markers of coagulation activation were observed (0--21%), which were dependent on filter type. None of the filters had a significant effect on von Willebrand factor (VWF) multimeric distribution or the activity of VWF and factors II, VII or X. The effect on levels of C3a appeared to be related to the filter surface charge: positively charged filters resulted in C3a generation, whereas negatively charged resulted in C3a removal. None of the observed changes are likely to be clinically significant unless subsequent processing of plasma (such as pathogen inactivation) results in further losses of coagulation factors.

Platelets expressing P-selectin and platelet-derived microparticles in stored platelet concentrates bind to PSGL-1 on filtrated leukocytes

The levels of interleukin-6 and platelet-derived microparticles (PMPs) were measured in the blood of 137 patients with side effects from platelet concentrate (PC) transfusion with leukocyte removal filtration, P-selectin-expressing platelet and PMPs in stored PC before and after the filtration, and filtered leukocytes positive for P-selectin glycoprotein ligand-1. The side effects, which were observed in 203 transfusions for 84 patients with hematologic disease and 53 patients with nonhematologic disease with no significant difference between the two groups, included urticaria (75.9%), erythema (18.7%), and fever (17.2%), but no anaphylactic reactions. The levels of interleukin-6 and PMP correlated in both groups, and were significantly higher in the hematologic disease group than in the nonhematologic disease group. The level of PMP, but not interleukin-6, was significantly higher for patients testing positive for allergic reaction than for those testing negative. In the stored PC prior to filtration, the level of interleukin-6 was normal. The level of P-selectin-expressing platelets and PMPs was elevated before filtration, but was significantly lower after filtration. Taken together, the results suggest that PMP is involved in the generation of transfusion reactions, and indicate that both platelets and PMP displaying P-selectin bind to P-selectin glycoprotein ligand-1 of leukocytes retained by the leukocyte filter.

Cytokines in WBC-reduced apheresis PCs during storage: a comparison of two WBC-reduction methods

BACKGROUND

Several studies have suggested that cytokine accumulation during storage of platelet concentrates (PCs) may mediate nonhemolytic febrile transfusion reactions and that a reduction in WBC numbers prevents the generation of cytokines. Despite efforts to minimize WBC contamination in apheresis PCs, high numbers of WBCs and increased cytokine levels may still occur, depending on the quality of the apheresis device employed.

STUDY DESIGN AND METHODS

This study was undertaken to investigate whether PCs collected with WBC-reduction devices (Spectra LRS, COBE;or MCS+ LDP, Haemonetics) were sufficiently depleted of WBCs to limit cytokine accumulation during storage. The study evaluated 1) the levels of cytokines of WBC and platelet origin in two types of apheresis PCs during storage and 2) the effects of prestorage filtration on cytokine levels in the Spectra LRS PCs.

RESULTS

In the Spectra LRS PCs, low levels of IL-6, IL-8, and monotype chemoattractant protein 1 (MCP-1) were detected in Day 1 PCs, and they remained consistent during the shelf life. RANTES, platelet factor 4 (PF4), beta-thromboglobulin (beta-TG), and transforming growth factor (TGF)-beta1 were also detected in these PCs, and their levels increased significantly on storage. Prestorage filtration of Spectra LRS PCs did not further reduce the levels of IL-6, IL-8, MCP-1, PF4, beta-TG, and TGF-beta1 in the filtered component. In the MCS+ LDP PCs, IL-6 was detected on Day 1, and its level increased significantly on storage, whereas the levels in the Spectra PCs remained steady. IL-8 levels were lower in MCS+ LDP PCs than in Spectra LRS PCs of the same age. MCP-1 levels were similar in both products on Day 1 and marginally increased in stored MCS+ LDP PCs. Substantial amounts of RANTES, PF4, beta-TG, and TGF-beta1 occurred in Day 1 MCS+ LDP PCs, and, on storage, these levels rose significantly.

CONCLUSION

Despite a significant reduction in levels of WBC-derived cytokines, platelet-derived cytokines were present in different amounts in the two products.

Evaluation of pooled platelet concentrates using prestorage versus poststorage WBC reduction: impact of filtration timing

BACKGROUND

Concern for the undesirable consequences of transfusing passenger WBCs is leading to the general use of WBC-reduced platelet concentrates (PCs). However, the impact of prestorage versus poststorage WBC reduction on the quality of platelet products has not been clearly defined.

STUDY DESIGN AND METHODS

Pooled PCs were WBC reduced before or after 5-day storage, by use of a WBC filter (PXL-8, Pall Corp.). Samples from pools were taken on days 1 and 5, before and after filtration, and on Day 9 of storage and assessed for cell counts, biochemical values, expression of platelet glycoproteins, thrombin generation, and content of IL-6, IL-8, TNFalpha, transforming growth factor beta1 (TGFbeta1), and anaphylatoxins C3a and C4a.

RESULTS

Filtration of fresh and 5-day-stored pooled PCs via a PXL-8 filter was similarly efficient, rendering pools with low WBC counts (<1 x 10(6) cells) and high platelet recovery (>95%). No major changes were found in the metabolic behavior or the expression of platelet GPIb, GPIIb/IIIa, CD62, and CD63 in PCs filtered before or after storage. Filtration, either before or after storage, increased by less than 5 percent the proportion of CD62+ platelets. Moreover, no changes were found in the concentration of prothrombin fragments 1 and 2 and thrombin-antithrombin complexes in the pooled PCs derived from the time of filtration. Finally, prestorage WBC reduction abrogated the accumulation of IL-6 and IL-8, but it did not prevent that of anaphylatoxins C3a and C4a nor of TGFbeta1. However, filtration through a PXL-8 filter significantly reduced (40-90%) the amount of IL-8, C3a, and C4a in the filtrate.

CONCLUSIONS

The timing of PXL-8 filtration of PCs has little impact on the efficiency of WBC reduction and on platelet recovery, and it does not seem to affect the quality of platelets or the generation of thrombin in the PCs. As regards the goal of reducing the amount of bioactive products in PCs, it remains uncertain as to whether prestorage WBC reduction fully eliminates the need for poststorage filtration. Prestorage filtration leads to low levels of IL-6 and IL-8 in PCs, but it does not impair the poststorage content of TGFbeta1 or anaphyla-toxins. By contrast, poststorage PXL-8 filtration removes significant amounts of C3a and C4a, and thus it might provide clinical benefits beyond those of prestorage WBC reduction.

Pathophysiology of febrile nonhemolytic transfusion reactions

Most febrile nonhemolytic transfusion reactions (FNHTR) to platelets are caused by cytokines that accumulate in the product during storage. There have been numerous studies that have demonstrated high concentrations of leukocyte- and platelet-derived cytokines in stored platelet products. The mechanism of cytokine accumulation is not understood; however, recent studies have suggested that leukocyte apoptosis and/or monocyte activation during the manufacturing process may play a role. Additional support of cytokines as a cause of FNHTR is provided by a recently published randomized controlled trial that shows that removal of the supernatant plasma from platelets before transfusion significantly lowers the frequency of reactions and eliminates most of the severe reactions associated with platelet transfusions. Although cytokines appear to play a major role in causing platelet reactions, there is little evidence to support their role in causing erythrocyte reactions. Hence, it appears that most febrile nonhemolytic transfusion reactions to erythrocytes are probably the result of an incompatibility between leukocytes in the erythrocyte product and antibodies in the recipient's plasma. Recent studies have confirmed that the concentrations of proinflammatory cytokines in a wide variety of stored erythrocyte products are low. Also, there is no clinical evidence to suggest that the small quantities of cytokines present in stored erythrocyte products contribute to acute reactions to these products when transfused.

Quality and clinical response to transfusion of prestorage white cell-reduced apheresis platelets prepared by use of an in-line white cell-reduction system

BACKGROUND

This study evaluated the quality and clinical effectiveness of white cell (WBC)-reduced apheresis platelets collected by the use of a new technology, fluidized particle-bed separation.

STUDY DESIGN AND METHODS

In phase 1, six suitable donors underwent two separate plateletpheresis procedures on one occasion, each separated by less than 10 minutes. In random order, a control unit was collected with the COBE Spectra and a test unit with the Spectra Leukocyte-Reduction System (LRS). The quality of apheresis platelet components was assessed by an in vitro test panel, and residual WBCs were counted by Nageotte chamber and flow cytometric methods. For the in vivo studies, the test and control units were randomly labeled with either 51Cr or 111In at the end of storage and transfused simultaneously to the donor. Samples were taken for calculation of platelet survival and recovery. In phase II, 109 thrombocytopenic patients were given platelets collected by use of the Spectra LRS.

RESULTS

Test platelets had significantly fewer residual WBCs (median 7.6 x 10(4)) than control platelets (median 3.9 x 10(5)), with equivalent in vitro function values. Test and control platelets had similar recovery and survival. Transfused platelets collected by use of the LRS achieved a mean 1-hour corrected-count increment of 19.3.

CONCLUSION

The LRS collects platelet components with significantly lower WBC contamination without adverse effects on the function or in vivo survival of the platelets.

Effects of prestorage white cell reduction on platelet aggregate formation and the activation state of platelets and plasma enzyme systems

BACKGROUND

The introduction of prestorage white cell (WBC) reduction in random-donor platelet concentrates in Canada has increased the occurrence of particulate material in PCs. The effects of filtration on platelet activation state and the activation of plasma enzyme systems were assessed.

STUDY DESIGN AND METHODS

Particulate material was examined by light microscopy, electron microscopy, protein electrophoresis, and biochemical analysis. Thirty PCs (10 unfiltered, 20 filtered) were examined during processing and 5-day storage for pH, platelet count and mean volume, morphology, activation marker expression, and hypotonic shock response. Complement activation, thrombin generation, and fibrinolysis were assessed by using specific enzyme immunoassays or chromogenic assays.

RESULTS

By all analyses, the particulate material appeared to be platelet aggregates. Platelets exposed to WBC-reduction filters expressed a significantly higher level of activation markers CD62 and CD63, altered morphology, and increased platelet microparticles throughout the storage period than did unfiltered platelets. Complement activation at the C3 level was significantly increased in filtered units with little evidence of coagulation or fibrinolytic system activation.

CONCLUSION

Exposure of platelets to filters during prestorage WBC reduction increased platelet activation and mildly increased complement activation over the levels during the storage period. These alterations can contribute to the formation of irreversible platelet aggregates during processing.

Effects of filtration and gamma radiation on the accumulation of RANTES and transforming growth factor-beta1 in apheresis platelet concentrates during storage

BACKGROUND

Platelet-derived biologic response modifiers (BRMs) including RANTES and transforming growth factor (TGF)-beta1 accumulate in platelet components during storage because of platelet activation, and they may play a causative role in nonhemolytic febrile transfusion reactions. The majority of PCs with high unit values are provided by single donor apheresis in Japan.

STUDY DESIGN AND METHODS

RANTES and TGF-beta1 levels in platelet units prepared from single-donor apheresis platelet concentrates (apheresis PCs) and units from whole blood (buffy coat PCs) were investigated. The effects of prestorage and poststorage filtration and gamma radiation on the levels of RANTES and TGF-beta1 in the supernatant of apheresis PCs during storage were also examined.

RESULTS

The levels of RANTES and TGF-beta1 increased during storage from Day 0 to Day 5. The levels of RANTES and of TGF-beta1 correlated with the platelet concentration (p<0.01), but not with the residual white cell concentration in apheresis PCs that were not white cell reduced by filtration (p>0.05). In addition, there was a correlation between RANTES and TGF-beta1 levels (p<0.01). In white cell-reduced apheresis PCs using negatively charged filters as well as in gamma-radiated apheresis PCs, the levels of these two BRMs-did not differ at any storage time from those of untreated apheresis PCs. Filtration of apheresis PCs with negatively charged filters after 3 days of storage significantly (p<0.05) reduced the levels of RANTES, but not of TGF-beta1. There was no reduction in the levels of RANTES and TGF-beta1 levels by positively charged filters. The RANTES levels in buffy coat PCs were slightly higher than but not significantly different from those of apheresis PCs during storage, except for the level on Day 1. There were no differences in the TGF-beta1 levels in apheresis and buffy coat PCs during storage.

CONCLUSION

Prestorage filtration and gamma radiation had neither preventive effects on the accumulation of RANTES and TGF-beta1 nor adverse effects on platelet activation. Negatively charged filters might be useful for the reducing the levels of RANTES in stored apheresis PCs.

Complement and biocompatibility

Blood contact with foreign surfaces induces a certain degree of activation of the defence systems including complement. Recent data using complement specific inhibitors have shown that complement is not only associated with, but in fact contributes to the whole body inflammatory reaction seen as a complication of cardiopulmonary bypass (artificial surfaces) and is responsible for the hyperacute rejection of xenografts (foreign endothelium). Complement activation products, particularly the terminal SC5b-9 complex (TCC), is a sensitive indicator of bioincompatibility. Modifications of the artificial surfaces by coating with heparin improves both coagulation and complement compatibility. The use of specific complement inhibitors in general improves biocompatibility both of artificial materials and foreign endothelium.