Experimental animal model of refractoriness to donor platelets: the effect of plasma removal and the extent of white cell reduction on allogeneic alloimmunization

A complement-mediated rat xenotransfusion model of platelet refractoriness

BACKGROUND

Platelet refractoriness remains a challenging clinical dilemma although significant advancements have been made in identifying human leukocyte antigen (HLA) matched or HLA compatible units. Antiplatelet antibodies are the major risk factor for immune-mediated platelet refractoriness, yet the role of antibody-initiated complement-mediated platelet destruction remains poorly understood.

STUDY DESIGN AND METHODS

Human complement-mediated opsonization and killing of platelets was assayed ex vivo using antibody-sensitized human platelets incubated with complement-sufficient human sera. A new animal model of platelet refractoriness utilizing Wistar rats transfused with human platelets is described.

RESULTS

Human platelets sensitized with anti-platelet antibodies were rapidly opsonized with iC3b upon incubation in human sera. This opsonization could be completely blocked with a classical pathway complement inhibitor, PA-dPEG24. Complement activation decreased platelet viability, which was also reversible with complement inhibitor PA-dPEG24. A new rat model of platelet refractoriness was developed that demonstrated some platelet removal from the blood stream was complement mediated.

CONCLUSIONS

Complement activation initiated by anti-platelet antibodies leads to complement opsonization and decreased platelet viability. A new rat model of platelet refractoriness was developed that adds a new tool for elucidating the mechanisms of platelet refractoriness.

New Options for Multicomponent Collection (MCC) with the Latest Cell Separators

Recently, several new cell separators have become available for high platelet low WBC contamination thrombocytapheresis. In their original configuration, these apparatuses can only collect plasma along with platelets, while no concurrent red cell collection can be carried out. In this study, we present the preliminary results of plasma and/or erythrothrombocytapheresis after the adaptation of the lines of two different cell separators, namely the Fresenius AS 204 and the Baxter Health Care Amicus. In addition, the preliminary results of multicomponent collection using the Dideco Excel will be presented; in the latter a system of plasma recirculation was introduced, to increase the purity and quality of the platelet product. The results of these studies show that erythrothrombocytapheresis can be carried out with all these apparatuses, but only with Dideco-Excel and the Fresenius AS 204 the procedure is totally automated. There are marginal differences in the quality of the RBC product in terms of percent hematocrit, from 65% with the Excel and AS 204 to ∼ 75% with the Amicus and in terms total content of hemoglobin which averages 58 g per RBC concentrate when RBC collection is carried out during the processing of ∼ 420 ml of whole blood. In terms of platelet collection, the differences are presently moderate, as the platelet yield and WBC contamination are not affected by the concurrent RBC collection. The average platelet yield was 3.98-4.1, and 4.01x1011 and the total WBC contamination was 1.2-2.9, and 1.9X105 rerspectively with the Amicus, the AS 204 and the Excel. These represent a new step in the direction of total apheresis for blood and blood component procurement.

Acute Intravascular Hemolysis in Two Patients Transfused with Dry-Platelet Units Obtained from the Same ABO Incompatible Donor

Since 1989 we have been collecting dry-platelets on a routine basis. Dry-platelets are those collected along with 25–30 ml of contaminating plasma cell with separators such as the Amicus, AS 104 and the Excel Pro. Platelets are resuspended in non plasma media for storage and for at least 60 hours their viability and functionality are not impaired. In this article we report on two hemolytic crises determined by two O Rh D + units of single donor platelets (SPD) taken from the same donor in a double-apheresis session. The two split units were admistered to two A Rh D + patients suffering from metastatic breast cancer and severe aplastic anemia (SAA) respectively. In both cases the hemolytic reaction was of the intravascular type, with a drop in hemoglobin (Hgb) level from 8.6 to 5.4 and from 8.8 down to 5.3 g/dl respectively. From the patients’ RBC only α - agglutinins were eluted and donor's indirect antiglobulin test (IAT) was negative with extended panel RBCs. In the first case the clinical course after erythroexchange (Erex) was uneventful whereas in the second one, that suffering from SAA, after Erex, acute renal failure and shock did complicate the clinical course and the patient died seven days after the incriminated platelet transfusion.

Erythrothrombocytapheresis and Plasmathrombocytapheresis with Storage in T-sol of Platelets Collected by the New Amicus Cell Separator

The Amicus cell separator is the latest apparatus introduced into the international market for high-yield, low WBC contamination and short-procedure time thrombocytapheresis. In its original configuration the apparatus collects platelets for subsequent resuspension in plasma and no collection of PRBC can be carried out along with thrombocytapheresis. In this paper we present the results of plasma-thrombocytapheresis and erythro-thrombocytapheresis after the adaptation of the Amicus to the collection and storage of platelets in a non-plasma medium and the concurrent collection of PRBC. From our study it is concluded that PRBC collection doesn't modify the quality of the platelet product obtained from random donors (platelets pre-count 263×10e3/μl) in terms of yield which is 4.6×10e11 platelets, WBC contamination (1.3×10e5) or procedure time (63±26 min.). The quality of the platelet products is satisfactory too, as measured by aggregation induced by collagen and ristocetin or by the substantial stability of membrane glycoproteins (CD62 - 63 - 51 - 36 - 42B). The concentrate had an average content of 58.8 g of hemoglobin per bag, a final volume of 376 ± 13 ml, (after the addition of 100 ml of SAG-M) and a normal mechanic and osmotic fragility.

Leucocyte depletion of perioperative blood transfusion does not affect long-term survival and recurrence in patients with gastrointestinal cancer

BACKGROUND

Perioperative red blood cell (RBC) transfusion may be associated with a poor prognosis in cancer surgery. Allogeneic leucocytes are assumed to play a causal role. This study evaluated the long-term effect of transfusion with leucocyte-depleted (LD) blood in patients with gastrointestinal cancer.

METHODS

The Transfusion Associated Complications = Transfusion Induced Complications? (TACTIC) study is a multicentre randomized controlled trial evaluating the short-term benefits of LD versus non-LD RBC transfusions. The present study evaluated 5-year survival and cancer recurrence among 512 patients with gastrointestinal cancer included in the TACTIC study.

RESULTS

Some 89.2 per cent of patients had a primary tumour and 79.7 per cent underwent surgery with curative intent; 243 patients received perioperative RBC transfusion (median 3 units). The 5-year overall survival rate of patients with any type of gastrointestinal cancer was 50.8 per cent in the LD group and 45.8 per cent in the non-LD group (P = 0.191). Corresponding 5-year disease-free survival rates were 60.0 and 56.6 per cent (P = 0.482), and recurrence rates 32.9 and 34.3 per cent (P = 0.864).

CONCLUSION

Leucocyte depletion is not associated with better long-term survival and lower recurrence rates in patients with gastrointestinal cancer.

Evaluation of different methods of leukoreduction of donor platelets to prevent alloimmune platelet refractoriness and induce tolerance in a canine transfusion model

The effectiveness of different methods of leukoreduction in preventing alloimmune platelet refractoriness was evaluated in a canine model. Platelets from a random donor dog were administered for up to 8 weeks or until platelet refractoriness. Standard (STD; unmodified) platelets were accepted by 14% of recipients (n = 7) compared with 14% for centrifuge leukoreduced (C-LR) platelets (n = 21) and 31% for filter leukoreduced (F-LR) platelets (n = 13; no significant differences). Surprisingly, using both F-LR and C-LR platelets was highly effective (87% acceptance, n = 15). Transfusing F-LR/C-LR red blood cells (n = 4) or F-LR/C-LR plasma (n = 4), along with F-LR/C-LR platelets, did not affect platelet acceptance (100% acceptance). Overall acceptance of F-LR/C-LR platelets was 91% (n = 23; P < or = .05 versus STD, C-LR, or F-LR platelets). F-LR/C-LR transfusions also induced tolerance to subsequent STD platelet transfusions from the same donor (82% acceptance, n = 19) as well as to donor skin grafts without recipient immunosuppression (57% acceptance, n = 7). To evaluate mechanisms of tolerance induction, F-LR/C-LR platelets were gamma-irradiated. Although the gamma-irradiated F-LR/C-LR platelets were uniformly accepted (n = 6), tolerance to STD platelets was lost. These data suggest that some allostimulatory white cells are filter adherent, whereas others escape filtration but can be removed by centrifugation and tolerance requires a residual functioning white cell.

Anemia in the critically ill

The anemia of critical illness is a distinct clinical entity with characteristics similar to that of chronic disease anemia. Several solutions to the processes of anemia, such as blunted erythropoietin production and erythropoietin response and abnormalities in iron metabolism have been developed. The transfusion of RBCs provides immediate correction of low hemoglobin levels, which may be of value in patients with life-threatening anemia. Avoidance of RBC and blood component transfusion, however, is becoming increasingly important as data of adverse clinical outcomes in critically ill patients become clearer. Although the optimal hemoglobin in critically ill patients is not determined, this organ system has a generous reserve. Short-term compensated anemia is tolerated well, while exogenous erythropoietin allows patients to achieve higher hemoglobin concentrations without exposure to transfused blood/blood components. A recent randomized trial enrolled over 1300 critically ill patients to receive either 40,000 units of exogenous erythropoietin or placebo. These authors found that patients randomized to erythropoietin received significantly less allogeneic RBC transfusions and had significantly greater increases in hemoglobin. Although no differences were found between groups in gross clinical outcomes (ie, death, renal failure, myocardial infarction), this study did not have the power to identify small differences in outcomes. This and other studies of exogenous erythropoietin therapy in critically ill patients clearly demonstrate that the bone marrow in many of these patients will respond to the administration of erythropoietin despite their illness, suggesting a blunted production of erythropoietin rather than a blunted response to erythropoietin. Exogenous erythropoietin therefore represents a therapeutic option for treating anemia in critical illness. Acute events in medicine and surgery often lead to many patients becoming anemic. Solutions to this process of anemia should be focused on preventing such events. Anemia after surgery represents an area for prevention. Blood conservation strategies can be performed with adequate results. Monk et al randomized 79 patients undergoing radical prostatectomy to preoperative autologous donation (PAD), preoperative exogenous erythropoietin therapy plus ANH immediately following induction of general anesthesia, and ANH alone. This study concluded that all three techniques resulted in similar hemostasis outcomes (eg, bleeding and transfusion rates), but ANH alone was the least expensive, and ANH plus exogenous erythropoietin and ANH alone resulted in a higher ICU hematocrit compared with PAD. Regardless of these prophylactic strategies, patients still become anemic after surgery or during critical illness. This acute event anemia usually is treated with RBC transfusion; however, autologous blood recovery (cell salvage systems) has been shown to be effective in patients with acute bleeding-related anemia, and this may reduce patients' exposure to allogeneic blood in these patients. There are no universally accepted treatment guidelines for managing anemia, and practice differs between clinicians, hospitals, regions, and countries. Transfusion medicine is evolving and incorporating many new pharmacological agents into the armamentarium of anemia and bleeding therapy. Accumulating evidence suggests that anemia in critically ill patients is common and correlated with poor outcomes. The management of anemia can improve outcomes; however, the optimal management of anemia is not performed universally. New approaches, continued research, and an understanding of anemia may result in more consistent and improved outcomes for critically ill patients.

Comparison of platelet loss during leukocyte reduction at 4, 24, and 48 hours postcollection using a Closed System Apheresis Kit with Integral filter

Prestorage leukocyte reduction of platelet concentrates may reduce adverse effects of transfusion while affording better quality control. Platelets and leukocytes may undergo activation during storage, which could affect the performance of leukocyte reduction filters. The purpose of this study was to evaluate the efficiency of leukocyte reduction and concomitant platelet loss with a new apheresis kit with an integral leukocyte reduction filter. Twelve donors underwent plateletpheresis on three occasions using the CS-3000 PLUS Blood Cell Separator with the Access Management System and the Access Closed System Apheresis Kit with Integral Sepacell Leukocyte Reduction Filter and Double Return Line Needle (Baxter-Fenwal Division, Deerfield, IL). Of the three products from each donor, one each was filtered at 4, 24, and 48 hours after completion of the plateletpheresis. Mean prefiltration platelet count was 4.43 x 10(11) and mean postfiltration platelet count was 3.56 x 10(11). Mean platelet recovery at 4, 24, and 48 hours filtration was 75%, 83%, and 84%, respectively. Analysis of variance (ANOVA) demonstrated that platelet recovery with filtration at four hours was significantly less than with filtration at 24 hours (P = 0.0236) and filtration at 48 hours (P = 0.0122). Platelet recovery with filtration at 24 hours did not differ significantly from filtration at 48 hours (P = 0.7684). Mean prefiltration WBC count was 0.93 x 10(6) and mean postfiltration WBC count was 0.12 x 10(6). Efficiency of leukocyte reduction was not significantly related to when filtration was performed. There was no significant variation from donor in platelet recovery or in leukocyte reduction efficiency. This method of prestorage leukocyte reduction demonstrated slightly but statistically significantly better platelet recovery with filtration at 24 or 48 hours after platelet collection compared to four hours. All filtration times provided acceptable platelet yields with very low residual WBC.

Dry platelets with the Dideco Excel apparatus

Dry platelets are required to prevent hemolytic and nonhemolytic febrile reactions after transfusion to ABO mismatched recipients, to reduce the risk of HLA immunization and to prevent allergic or anaphylactic reactions. Previously we have shown that the collection of single donor platelets almost free of plasma is possible with different cell separators. With the systems we described for the CS 3000+/Amicus and AS 104-204 apparatuses collection of dry platelets implies their resuspension in non plasma solutions after opening the circuit. With the new system developed by Dideco for the Excel apparatus this moreover is no longer required since the platelet bag can be connected to the resuspending medium through a dedicated line with an antibacterial filter. Platelets are collected cyclically and the resuspending solution is added when the procedure is over. In this study 53 collections were evaluated, 21 of which were erythrothrombocytapheresis. In 60-65 min 4.21 of anticoagulated blood (1/12) were processed with platelet collection automatically done after 6-700 ml cycles. The platelet yield averaged 4.67 +/- 0.7 x 10(11), with a platelet efficiency per minute of 7.18 +/- 0.9 x 10(9). The WBC contamination averaged 2.6 +/- 0.7 x 10(5) and contamination did not exceed 0.87 x 10(6). The quality of platelets was satisfactory as measured by aggregation, morphology score, and CD 62 membrane glycoprotein externalization. These results were comparable to those obtained with three other Excel apparatuses used in the conventional way to collect platelets resuspended in plasma or with the Amicus used to collect dry platelets using an open system.

Clinical trial and local process evaluation of an apheresis system for preparation of white cell-reduced platelet components

BACKGROUND

A new method for the consistent preparation of white cell (WBC)-reduced plateletpheresis components, the Spectra Leukoreduction System (LRS), was evaluated by clinical trial and local process validation. The centrifuge-based system was projected to decrease the WBC content of plateletpheresis components to a level below 1 x 10(6) per unit. Phase I and II clinical trials were performed. The manufacturer's claims were then tested at the local level with an ongoing quality assurance program.

STUDY DESIGN AND METHODS

In Phase I, a cross-over analysis of five subjects compared LRS to standard plateletpheresis procedures in collection efficiency and component quality: a panel of in vitro measures was taken on Day 0 and Day 5. In Phase II, the LRS process was tested on a larger scale (n = 57; control = 58) with component transfusion. Finally, validation, determination of degree of conformance with standards, and ongoing quality control were performed locally on a newly installed instrument.

RESULTS

Phase I and II trials revealed no significant differences between LRS and control units in donor or recipient safety and comfort, platelet function and yield, or component volume. WBC per-unit values were significantly different: the LRS median per unit was 3.2 x 10(4) WBCs, versus 81.4 x 10(4) for control units. Assessment of process capability gave an estimate of 99-percent confidence that 99.5 percent of LRS units would be WBC reduced to < 1 x 10(6) WBCs. Local process validation and quality control revealed 90-percent confidence that 99 percent of the units would be WBC reduced and 99.9-percent confidence that 75 percent would exceed platelet yield standards; the process was stable over time.

CONCLUSIONS

The LRS is safe for apheresis and the component produced is safe for transfusion with platelet function and yield equivalent to controls and WBC reduction superior to controls. Local process evaluation confirmed that component quality meets the goals of the institution.

Multicomponent Collection (Mcc): An Overview

Collection of multiple products, including single and double units of platelets (SDP, DPP), plasma and RBC is progressively improving donor utilization and is leading to more cost-effective apheresis. Cell separators such as the Fresenius AS 204, the Dideco Excel version 97 and the Baxter Amicus are newcomers to the family of the last generation apparatuses used for MCC such as the AS 104, the Vivacell and the MCS 3p. The Cobe Spectra is for the moment the only apparatus unable to collect packed RBC along with platelets but Cobe too is moving in the direction of MCC. The next step is triple product apheresis.

Transfusion and stem cell support in cancer treatment

Intensification of therapeutic regimens, improved patient survival, and advances in cytokine and cellular therapies have led to increasingly complex requirements for transfusion and stem cell support in cancer treatment. This article focuses on current and evolving issues in red blood cell, platelet, and granulocyte transfusion support, as well as measures to avoid increasingly important complications of transfusion therapy, such as alloimmunization, graft-versus-host disease, cytomegalovirus infection, and immunomodulation. Issues concerning current applications of hematopoietic stem cell transplantation and future prospects also are discussed.

Transfusion strategies: opportunities for improvement

Opportunities for improving transfusion practice that involve patient care, technological advancements, and technology changes in the clinical arena are discussed. Patient care should be enhanced by optimizing transfusion therapy and the source of donors of platelet concentrates, i.e., single donor platelets (obtained by plateletapheresis from a single donor) or to random donor platelets (containing a pool of six to eight platelet concentrates separated from whole blood donations). The availability of "third-generation" leukocyte-reduction filters provides the technology for significantly and consistently providing leukocyte-reduced blood components. The potential benefits of using these filters is presented. Platelet crossmatching represents a technology change involving clinical practice. Suggestions for incorporating this test into platelet transfusion algorithms are included.

Evaluation of apheresis platelet concentrates collected with a reduced (30-ml) collection chamber with resuspension and storage in a synthetic medium

Recently, the CS-3000 Plus Blood Cell Separator with the TNX-6 platelet separation chamber insert has been furnished with a small-volume (30-ml) collection chamber. In this study, a platelet synthetic medium containing glucose and bicarbonate (PSM) was used for resuspension and storage of this highly concentrated platelet product. Eighteen donors participated in a paired study design where each participant donated platelets on two occasions, once following collection in a standard chamber with resuspension and storage in plasma and once following collection in the new chamber with resuspension and storage in PSM. Substantially higher total platelet counts were obtained using platelets collected in the small chamber and stored in PSM as compared to control (4.4 +/- 0.9 x 10(11) vs. 3.5 +/- 0.9 x 10(11) platelets, p < 0.01 by paired t test). After 5 days of storage, PSM-stored platelets demonstrated higher ATP levels, less lactate dehydrogenase in the supernatant and increased lactate production with resulting lower pH at day 5 of storage (6.94 +/- 0.15 vs. 7.08 +/- 0.09, p < 0.05). There were no statistically significant differences of the survival by multiple-hit estimation of PSM-stored as compared to plasma-stored platelets as determined by 111In labeling and infusion. A slight decrease in the initial percent recovery with the additive-suspended as compared to suspended plasma cells was noted: 50 +/- 8 versus 54 +/- 9%, respectively (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)