The safety of weekly plateletpheresis: effect on the donors' lymphocyte population

T-cell lymphopenia in frequent volunteer platelet donors

In the United States, more than 2 000 000 apheresis platelet units are collected annually from volunteer donors. Platelet donors in the United States and elsewhere are permitted to donate up to 24 times per year. Recently, frequent apheresis platelet donation has been associated with severe T-cell lymphopenia. Several frequent platelet donors have been found to have peripheral blood CD4+ T-cell counts below 200 cells/µL, the threshold for AIDS in HIV-positive individuals. Independent risk factors for plateletpheresis-associated lymphopenia include lifetime donations, age, and donations on the Trima Accel instrument (Terumo BCT), which uses a leukoreduction system (LRS) chamber to trap white blood cells. Less often, severe lymphopenia can occur in donors collected on the Fenwal Amicus instrument (Fresenius Kabi), which has no LRS. For Trima Accel donors, lymphopenia can be partially mitigated by performing a plasma rinseback step at the end of collection. To date, there is no definitive evidence that plateletpheresis-associated lymphopenia is harmful. In a study of frequent platelet donors with lymphopenia who were administered COVID-19 messenger RNA vaccines, immune responses were normal. The homeostatic mechanisms responsible for maintaining a normal peripheral blood T-cell count remain obscure, as do the causal mechanisms underlying plateletpheresis-associated lymphopenia.

Serial analysis of hematological, biochemical, and immunological parameters alterations in regular healthy voluntary donors during plateletpheresis donation

BACKGROUND AND OBJECTIVES

The long-term effect of regular plateletpheresis on donors has not been characterized. Hence, we planned to study the long-term alterations in hematological, biochemical, and immunological parameters in regular repeat platelet apheresis donors.

MATERIALS AND METHODS

Thirty-three healthy voluntary regular repeat apheresis donors presenting for platelet donation, fulfilling the requisite donor selection criteria, underwent sequential analysis of the hematological, biochemical, and immunological parameters over 1 year.

RESULTS

A total of 33 regular repeat donors were enrolled in the study; out of these, 22 could be followed up to 3 months, 12 up to 6 months, and 10 donors up to 12 months for their hematological, biochemical, and immunological parameters. Overall, there was no significant change in hematological profile except a rise in platelet count at 3 months (P = 0.023) with no significant difference at 6 and 12 months from the baseline. In addition, serum thrombopoietin levels at 3 months (P = 0.010) and serum erythropoietin at 6 months (P = 0.01) were significantly higher than baseline. Mean platelet volume was significantly higher from baseline at 12 months (P = 0.00). Serum protein, lymphocyte subpopulation, and serum ferritin did not show any significant change from baseline over 12 months of follow-up. However, there was a significant decline (P = 0.00) in serum calcium and an increase in serum magnesium from baseline (P = 0.03) at 12 months.

INTERPRETATIONS AND CONCLUSIONS

To conclude, apheresis platelet donation is a safe procedure. However, a complete hematological, biochemical, immunological profile and bone marrow density at regular intervals (3-6 months) are recommended to ensure the safety of regular repeat plateletpheresis donors.

Total platelet donation count and donation frequency are determinants of plateletpheresis-associated lymphopenia

BACKGROUND

Plateletpheresis using a leukocyte reduction system (LRS) traps donor WBCs in the LRS chamber, which may lead to lymphopenia, especially in frequent plateletpheresis donors. It seems plausible that this might cause adverse effects. However, current knowledge about potential confounders and donor health impacts is incomplete.

DONORS AND METHODS

Recent platelet donors and donations collected at University Hospital Regensburg from 2016 to 2019 using the Terumo BCT Trima Accel LRS system were retrospectively analyzed and compared with historical platelet donors and donations collected mainly with Fresenius Kabi Amicus non-LRS system from 2010 to 2013. Additionally, recent donors were prospectively surveyed using a health-related topics questionnaire.

RESULTS

Analysis of 819 recent donors with 11,254 blood counts and 1464 questionnaires and 1011 historical donors with 12,848 blood counts revealed that increased annual platelet donation frequencies were associated with decreased lymphocyte counts in both groups. Median lymphocyte counts in recent donors with no versus ≥24 previous annual donations declined from 2.0 to 1.2 × 10³ /μL (p < 2.2 × 10^-16 ), and those in historical donors with no versus ≥24 previous annual donations decreased from 2.0 to 1.5 × 10³ /μL (p = 6 × 10^-4 ), respectively. The questionnaire results showed that donation frequency and lymphopenia were not associated with upper respiratory tract infection (URTI) incidence or duration, but platelet donors who concomitantly donated granulocytes had significantly shorter URTI durations than those who did not (p = .008).

CONCLUSION

This study confirmed that plateletpheresis-associated lymphopenia occurs in LRS and to a lesser degree in non-LRS platelet donors, but revealed no evidence of a negative impact on donor health.

Frequent platelet donation is associated with lymphopenia and risk of infections: A nationwide cohort study

BACKGROUND

Recently, plateletpheresis donations using a widely used leukoreduction system (LRS) chamber have been associated with T-cell lymphopenia. However, clinical health consequences of plateletpheresis-associated lymphopenia are still unknown.

STUDY DESIGN AND METHODS

A nationwide cohort study using the SCANDAT3-S database was conducted with all platelet- and plasmapheresis donors in Sweden between 1996 and 2017. A Cox proportional hazards model, using donations as time-dependent exposures, was used to assess the risk of infections associated with plateletpheresis donations using an LRS chamber.

RESULTS

A total of 74 408 apheresis donors were included. Among donors with the same donation frequency, plateletpheresis donors using an LRS chamber were at an increased risk of immunosuppression-related infections and common bacterial infections in a dose-dependent manner. While very frequent donors and infections were rare in absolute terms resulting in wide confidence intervals (CIs), the increased risk was significant starting at one-third or less of the allowed donation frequency in a 10-year exposure window, with hazard ratios reaching 10 or more. No plateletpheresis donors that used an LRS chamber experienced a Pneumocystis jirovecii, aspergillus, disseminated mycobacterial, or cryptococcal infection. In a subcohort (n = 42), donations with LRS were associated with low CD4+ T-cell counts (Pearson's R = -0.41; 95% CI, - 0.63 to -0.12).

CONCLUSION

Frequent plateletpheresis donation using an LRS chamber was associated with CD4+ T-cell lymphopenia and an increased risk of infections. These findings suggest a need to monitor T-lymphocyte counts in frequent platelet donors and to conduct future investigations of long-term donor health and for regulators to consider steps to mitigate lymphodepletion in donors.

CD4+ T-cell lymphopenia in frequent platelet donors who have ceased platelet donation for at least 1 year

BACKGROUND

We recently discovered that 30% of current frequent apheresis platelet donors in a study at our donor center had CD4+ counts below 200 cells/μL. How long CD4+ lymphopenia persists after ceasing plateletpheresis is unknown. Whether there are infectious or other complications in former frequent donors that could relate to CD4+ lymphopenia is also unknown.

STUDY DESIGN AND METHODS

We mailed a letter to former frequent apheresis platelet donors who had not donated platelets for at least 12 months. Frequent donation was defined as 20 to 24 plateletpheresis sessions in at least one 365-day period starting in 2011. Donors who expressed interest in the study were contacted to schedule a study visit. Participants in the study provided a blood sample and completed a health questionnaire that included questions about opportunistic infections and malignancies.

RESULTS

Of 50 potential study candidates who were mailed a letter, 15 participated in the study. There were 2 participants with CD4+ counts below 200 cells/μL, one of whom had prior counts that documented a small improvement with cessation of plateletpheresis. Three participants had counts between 200 and 300 cells/μL. No study participant had a history of an opportunistic infection or a malignancy associated with immune dysregulation.

CONCLUSION

We detected CD4+ lymphopenia in former frequent apheresis platelet donors who had ceased platelet donation for more than 1 year. There was no evidence that the CD4+ lymphopenia predisposes to opportunistic infections or to malignancies associated with immune dysregulation.

Plateletpheresis-associated lymphopenia in frequent platelet donors

More than 1 million apheresis platelet collections are performed annually in the United States. After 2 healthy plateletpheresis donors were incidentally found to have low CD4+ T-lymphocyte counts, we investigated whether plateletpheresis causes lymphopenia. We conducted a cross-sectional single-center study of platelet donors undergoing plateletpheresis with the Trima Accel, which removes leukocytes continuously with its leukoreduction system chamber. We recruited 3 groups of platelet donors based on the total number of plateletpheresis sessions in the prior 365 days: 1 or 2, 3 to 19, or 20 to 24. CD4+ T-lymphocyte counts were <200 cells per microliter in 0/20, 2/20, and 6/20 donors, respectively (P = .019), and CD8+ T-lymphocyte counts were low in 0/20, 4/20, and 11/20 donors, respectively (P < .001). The leukoreduction system chamber's lymphocyte-extraction efficiency was ∼15% to 20% for all groups. Immunophenotyping showed decreases in naive CD4+ T-lymphocyte and T helper 17 (Th17) cell percentages, increases in CD4+ and CD8+ effector memory, Th1, and regulatory T cell percentages, and stable naive CD8+ and Th2 percentages across groups. T-cell receptor repertoire analyses showed similar clonal diversity in all groups. Donor screening questionnaires supported the good health of the donors, who tested negative at each donation for multiple pathogens, including HIV. Frequent plateletpheresis utilizing a leukoreduction system chamber is associated with CD4+ and CD8+ T-cell lymphopenia in healthy platelet donors. The mechanism may be repeated extraction of these cells during plateletpheresis. The cytopenias do not appear to be harmful.

Evaluation of the performance of Trima Accel® v5.2 for the collection of concentrated high-dose platelet products and concurrent plasma from high platelet count donors, in Germany

BACKGROUND AND OBJECTIVES

This study was undertaken to test the ability of Trima Accel® version 5.2 to simultaneously collect concentrated high-dose leukoreduced platelet products and double doses of plasma.

MATERIALS AND METHODS

Random volunteers (18-65 years of age) with preprocedure platelet counts above 270 × 10(3) /μl were recruited among the blood center's apheresis donors. All complied with the center's donor selection criteria.

RESULTS

One hundred fourteen (114) collections were performed. Depending on which definition of single platelet dose is used (2.0 × 10(11) as prevalent standard in most European countries, and 3.0 × 10(11) as prevalent standard in the United States and Canada) in 107/114 (single dose = 2.0 × 10(11) ) and 39/114 (single dose = 3.0 × 10(11) ) instances, a triple platelet product was obtained. In 87 cases (76%), a double plasmaproduct (>430 ml) was collected, and in seven cases (6%), a single plasma product (>220 ml) was collected. In 20 procedures, only platelets without concurrent plasma were collected (18%). Overall procedure time was 87 ± 13 min and average platelet yield per procedure was 8.5 ± 1.4 × 10(11) (final storage concentration, 1,279 ± 153 × 10(3) /μl). The median residual leukocyte content per transfusion dose was 0.13 × 10(6) (0.02-0.98 × 10(6) ) for a single dose of 2.0 × 10(11) and 0.14 × 10(6) (0.02-0.98 × 10(6) ) for a single dose of 3.0 × 10(11) .

CONCLUSIONS

Trima Accel® version 5.2 allows for collection of concentrated high yield platelet products. It offers high productivity and reliably achieves the configured yield targets. Leukoreduction performance complied with both US and EU legal requirements. Collection as hyperconcentrates furthermore allowed for concurrent collection of double dose plasma in the majority of the procedures.

The effect of continuous-flow automated plateletpheresis on fibrinolytic activity of donor plasma

Blood circulating in extracorporeal circuit of the apheresis sets has a contact with an artificial surface. The data on the influence of plateletpheresis on fibrinolytic activity are very limited and difficult to interpret. The aim of our study was to estimate the effect of plateletpheresis on the activation of fibrinolysis. Plateletpheresis was performed in 17 healthy blood donors using continuous-flow cell separator COM.TEC (Fresenius, Bad Homburg, Germany). Before and after plateletpheresis, blood samples were taken and markers of fibrinolysis (PAP, t-PA, PAI-1) as well as factor XII activity have been measured. We observed statistically significant decrease in t-PA and factor XII activities after plateletpheresis. There were no significant changes in concentrations of t-PA, PAI-1 and PAP as well as PAI-1 activity after plateletpheresis. Plateletpheresis performed by COM.TEC cell separator has very little, if any, effect on the activation of fibrinolysis. The mechanism of the inhibition of t-PA activity needs further investigations.

Mononuclear cell variability and recruitment in non-cytokine-stimulated donors after serial 10-liter leukapheresis procedures

BACKGROUND

We introduced monitoring of mononuclear cell (MNC) counts to obtain enhanced donor control and a stable quality of MNC products, because there are limited data available about blood donors after serial leukapheresis (LP) procedures.

STUDY DESIGN AND METHODS

In a prospective paired study, 13 male healthy blood donors underwent 10-L LP procedures performed on two apheresis devices by use of two MNC program settings (COBE Spectra, Gambro BCT, SF 250 vs. SF 500; and AS.TEC 204, Fresenius Hemocare, CP 129 vs. CP 194). Donors' pre- and postdonation MNC counts were analyzed by fluorescence-activated cell sorting.

RESULTS

After each 10-L LP procedure, a transient decline (p < 0.05) of CD14+ monocyte and platelet counts appeared in donors. Loss of donors' CD3+ T cells, CD19+ B cells, and CD16+56+ natural killer (NK) cells during MNC collection was partly compensated by cell recruitment. The MNC recruitment factor (RF) seems to be higher with high-yield MNC program settings. Negative correlations (p < 0.01) were noticed between predonation counts and RFs of CD3+ T cells and CD16+56+ NK cells. Four serial 10-L LP procedures did not result in long lasting MNC depletion for donors.

CONCLUSION

MNC recruitment seems to depend on MNC program settings and collected cell yields. Low MNC counts could result in high cell recruitment that may contribute to stable collection results to some degree. Nevertheless, there seems to be a considerable individual variation of MNC recruitment in donors that should be investigated in more detail.

Safety issues of plateletpheresis: comparison of the effects of two cell separators on the activation of coagulation, fibrinolysis, and neutrophils and on the formation of neutrophil-platelet aggregates

BACKGROUND

Although many donors undergo repeated plateletpheresis, data on the consequences of plateletpheresis for the donor's health remain scarce. Thus, the effect of plateletpheresis on the activation of coagulation, fibrinolysis, and neutrophils was investigated.

STUDY DESIGN AND METHODS

Part 1: Sixteen healthy men were randomly assigned to undergo plateletpheresis on a cell separator (AMICUS, Fenwal Baxter; or MCS 3p, Haemonetics). The effects of plateletpheresis on plasma levels of prothrombin fragment (F(1+2)), D-dimer, plasmin-plasmin inhibitor (PPI) complexes, and plasminogen activator inhibitor (PAI-1); on the activation of neutrophils (% L-selectin+); and on the frequency of platelet-neutrophil aggregates (% CD41+ neutrophils) were compared. Part 2: Ten healthy men received infusions of ACD-A and placebo without apheresis in a randomized, double-blind crossover study to control for the pharmacologic effects of citrate.

RESULTS

Part 1: No change in F(1+2) occurred (p>0.05), which indicated that plateletpheresis did not enhance coagulation. Levels of D-dimer, PPI, and PAI-1 decreased over time on the AMICUS (p<0.001). Plateletpheresis did not activate neutrophils (p>0.05), but it decreased the percentage of CD41+ neutrophils (p<0.003). An approximately 80-percent drop in mononuclear cells was observed in the extracorporeal circulation of the AMICUS (p<0.001 vs. baseline and p = 0.005 vs. MCS 3p), and circulating lymphocyte and monocyte counts decreased concomitantly. Part 2: Infusion of ACD-A slightly decreased D-dimer levels (p<0.05), and both infusions decreased the circulating lymphocyte counts.

CONCLUSION

Plateletpheresis can be regarded as safe with respect to the activation of coagulation or neutrophils. The consequences for the donor's health of the decrease in D-dimer, PPI, and PAI-1 may deserve further investigation.

Effect of long-term platelet donation on lymphocyte subsets and plasma protein concentrations

Previous studies of changes in immune function in platelet donors have investigated subjects who were undergoing plateletpheresis using older equipment that is no longer in general use. Therefore, the purpose of this study was to determine the effect of long-term platelet donation on lymphocyte numbers and subsets and plasma protein concentrations in platelet donors using newer cell separators. Three groups included in the study were nondonor controls (n = 27), long-term whole blood donors (n = 29), and long-term platelet donors (n = 20). Using a cross-sectional analysis, lymphocyte numbers and subsets were determined and compared among the three groups. Plasma concentrations of total protein, globulin, albumin, and IgG were also compared. Among the three groups there were no significant differences in total white blood cell counts, percentage or absolute number of lymphocytes, or percentage or absolute number of lymphocyte subsets. Serum total protein, globulin, albumin, and IgG concentrations of platelet donors were within normal ranges. These data support the current Food and Drug Administration (FDA) and American Association of Blood Banks' standards for the frequency of platelet donation allowed and monitoring required for plateletpheresis donors. Furthermore, these data indicate that the FDA could eliminate the requirement for the warning in informed consents about lymphocyte depletion in platelet donors.

The collection of platelets by apheresis procedures

Collection of platelets by apheresis has been a major advance in transfusion medicine. It has allowed the supply of a therapeutically beneficial component to grow with medical needs. Donors find fulfillment in more frequent donations than are possible with whole blood and know that their donation fills a special need. New technology allows leukocyte reduction in the collection of the component with or without the use of filtration. Matching for refractory patients is possible. However, platelets collected by apheresis have not been shown to be hemostatically different from platelets separated from whole blood donations, and thus, do not represent an advance in therapeutic efficacy. The use of apheresis platelets does reduce donor exposure, but this has not been shown to be a safety advance, although it seems intuitively obvious that transfusion risk is statistically reduced in some patients requiring only a few platelet transfusions. Support of patients by apheresis platelets may or may not reduce the risk of alloimmunization. Apheresis platelets from some equipment have less white blood cell contamination even in the absence of filtration, which may be an advantage. Apheresis platelets could be a major step in the ultimate customization of blood collection, in which some donors would preferentially donate red blood cells, whereas others would donate platelets or plasma depending on their blood type and ability to donate frequently, and the current medical need of their donation. Perhaps this would be the most significant advance from the medical progress initiated by Cohn almost 50 years ago.

Effects on donors of repeated leukocyte losses during plateletpheresis

All blood components collected by automated cytapheresis contain donor leukocytes. The possibility that repeated cytapheresis donation might lead to clinically important leukocyte losses and immunodeficiency has been a long-standing concern. Although convincing data do not exist to substantiate this concern, it is common practice to limit the number of annual cytapheresis donations per donor and to monitor donors for developing lymphocytopenia. Clinically significant immunodeficiency is unlikely to occur unless donors lose > 1 x 10(11) lymphocytes within a few weeks period of time or unless donor lymphocyte counts fall persistently to < 0.5 x 10(9)/L. Each plateletpheresis procedure, when performed using modern cell separators that are designed to produce a relatively "pure" platelet concentrate, leads to the loss of 1.0 x 10(6) to 5.0 x 10(7) leukocytes. Thus, automated plateletpheresis as performed in 1994 is extremely unlikely to cause clinically significant lymphocyte depletion and consequent immunodeficiency.

In vitro study of immunologic changes in long-term cytapheresis donors

Several in vitro measurements of immune function were examined retrospectively in a population of active long-term cytapheresis donors (group I; n = 50) and the results were compared to age- and sex-matched controls (group II; n = 50) who had donated only whole blood. In group I, significantly different mean absolute lymphocyte counts (P = .0025), total T-cells (P = .0026) and T-helper cells (P less than .0001), and helper-to-suppressor ratios (P = .0279) were present. No differences were noted between the two groups for peripheral blood mean B-cell count, T-suppressor numbers, lymphocyte responsiveness to mitogens or alloantigen, and serum immunoglobulin level. The reduced mean absolute lymphocyte count in group I was due to the reduction in T-helper cell numbers and accounted for the imbalance in the helper-to-suppressor ratio. These disturbances are currently unexplained and, while no clinical consequences have so far become evident, there is a need to continuously monitor the immunologic status of cytapheresis donors. It is also important to determine whether reversal of the defects occurs and, if so, over what time interval.

Treatment of von Willebrand's disease and hypofibrinogenemia with single donor cryoprecipitate from plasma exchange donation

Conventional replacement therapy for hypofibrinogenemia and von Willebrand's disease requires multiple donor exposures and a correspondingly high risk of blood-borne infection. We describe the collection and successful use of cryoprecipitate derived from a single donor by plasma exchange donation to support such patients through major hemostatic stresses. The father of an epileptic patient with von Willebrand's disease produced cryoprecipitate containing 23,546 units of von Willebrand factor (vWF) in nine desmopressin-stimulated donations; this provided total factor replacement for neurosurgery to remove a seizure focus. The average yield was 2,616 units per donation and the average VWF concentration in cryoprecipitate was 17.7 units/ml. The husband of a hypofibrinogenemic patient with a history of postpartum hemorrhage provided cryoprecipitate containing 13.4 g of fibrinogen in five donations; this supported his wife through parturition without recourse to other blood products. The average yield was 2.7 g per donation, and the average fibrinogen concentration was 15.3 g/liter. Plasma exchange donation is a practical alternative source for cryoprecipitate. It can provide vWF and fibrinogen that carry a reduced risk of infectious disease transmission.

Lymphocyte subpopulations of plateletapheresis products collected with the Fenwal CS-3000 Cell Separator

To determine whether any lymphocyte subset is preferentially harvested and transfused as a consequence of plateletapheresis with the Fenwal CS-3000 Blood Cell Separator, the proportions of lymphocyte subpopulations in platelet concentrates were compared to their proportions in the donors' peripheral venous blood immediately prior to platelet collection. There was no difference in the proportion of B cells (surface immunoglobulin positive), T cells (OKT3 positive), helper/inducer T cells (OKT4 positive), suppressor/cytotoxic T cells (OKT8 positive), and natural killer cells (Leu 7 positive) in the donors' peripheral venous blood and the plateletapheresis product. Thus, although previous studies have demonstrated the ability to separate lymphocyte subpopulations by density centrifugation and velocity sedimentation, plateletapheresis with the CS-3000 harvests the lymphocyte subpopulations studied in the same proportions in which they circulate in donors' peripheral venous blood.

Mononuclear cell (MNC) collection by continuous-flow centrifugation (CFC)

Mononuclear cell separation and collection by continuous-flow centrifugation relates to centrifugal acceleration, total blood processed, peripheral blood concentration, and probable mobilization from extravascular sites during the procedure. At low-G forces, 70-80% of mononuclear cells are cleared. As G forces are increased, 95-100% of mononuclear cells can be cleared, but excessive platelet depletion occurs. An average of three billion cells were harvested from 2-3 liters of blood, rising to nine billion when 6 liters were processed. The total blood processed is defined by citrate infusion rates and ionized calcium changes. Large quantities of mononuclear cells were collected from normal donors without any significant depletion. If the objective of harvesting mononuclear cells is depletion, intensive schedules may be needed.

Optimization of parameters for maximization of plateletpheresis and lymphocytapheresis yields on the Haemonetics Model V50

Automated apheresis techniques afford the opportunity of tailoring collection parameters for each donor's hematologic profile. This study investigated the effect of various settings of the volume offset parameter as utilized in the Haemonetics Model V50 instrumentation during platelet- and lymphocytapheresis to optimize product yield, purity, and collection efficiency. In both types of procedures, increased product yield could be obtained by using an increased volume offset for donors having lower hematocrits. This improvement was related to an increase in collection efficiency. Platelet products also contained fewer contaminating lymphocytes with this approach. Adjustment of the volume offset parameter can be utilized to make the most efficient use of donors and provide higher-quality products.

Immune function in blood donors following short-term lymphocytapheresis

Lymphocyte losses occur during repeat plateletpheresis and/or leukapheresis procedures and are potentially harmful to normal host immune function. This concern prompted us to study the effect of repeat lymphocytapheresis (lymphapheresis) on the immune system of healthy blood donors. Following a total of six lymphapheresis procedures over a 12-day period with removal of a mean of 41.6 X 10(9) lymphocytes, there were no significant changes in donor (n = 5) absolute lymphocyte counts, quantitative immunoglobulin levels or immune response capability as assessed by the following in vitro assays: percent of E, EA, and EAC rosette-forming cells, the percent of surface membrane immunoglobulin bearing cells, and the blastogenic responses to stimulation with phytohemagglutinin, pokeweed mitogen and concanavalin A. The procedures were well-tolerated without complications. During a follow-up period of 18 months, significant increases in total white cell counts (but not absolute lymphocyte counts), and in quantitative immunoglobulin levels (IgG, IgM, and IgA) were observed. The median increases in immunoglobulin levels ranged from 27.5% for IgG to 44% for IgA. We conclude that lymphapheresis as described is relatively safe and our results are reassuring in relation to lymphocyte losses that may occur during repeat cytapheresis procedures of normal blood donors.

Peripheral blood lymphocyte numbers, lymphocyte proliferative responses in vitro, and serum immunoglobulins in regular hemapheresis donors

Selected tests of lymphoid function were used to screen a population of volunteer hemapheresis donors. Testing included: 1) absolute lymphocyte numbers, and percentage of T-cell, B-cell, and mononuclear phagocytes, 2) serum immunoglobulins, and, 3) in vitro proliferative responses to lectin mitogens (phytohemagglutinin, concanavalin A, and pokeweed mitogen), soluble antigens (staphylococcal filtrate, candida, and streptococcal varidase), and cell-bound alloantigens (mixed lymphocyte culture). A control population of first-time plateletpheresis donors was examined similarly. Regular donors manifested a small but statistically significant decrease in absolute lymphocyte counts (p less than 0.02), and IgM (p less than 0.02) compared to controls. Leukapheresis donors also manifested significant decreases in percentage of T cells (p less than 0.02). These findings are qualitatively similar to changes reported following intensive lymphocytapheresis and indicate the need for conservative policies regarding donation frequency in hemapheresis programs.

Apheresis donor safety--changes in humoral and cellular immunity

Modern techniques of mechanical hemapheresis have made it possible to selectively remove vast quantities of lymphocytes and plasma immunoglobulins, and the concentration of these substances in donor blood can fall below the normal range. It is feared that this may lead to immunosuppression; a condition associated in some clinical settings with infections, malignancy and autoimmune diseases. Using primary immunodeficiency diseases and induced immunodeficiency states (for example, therapeutic lymphocytapheresis, chronic thoracic duct drainage and intestinal lymphangiectasia) as models to judge competency of the immune system, it can be predicted that body defense mechanisms can become defective when serum IgG levels are less than 200 mg/dl or the blood lymphocyte count is less than 1000/microliter. However, impaired immunologic function can occur in the presence of normal quantities of these substances in the blood stream; conditions that may be related either to imbalances of immune regulatory factors or to qualitative (rather than quantitative) abnormalities of the immune system. A number of investigators have documented the losses of lymphocytes and plasma immunoglobulins incurred by donors experiencing mechanical hemapheresis. In addition, both the immediate and long-term decreases in the concentration of these substances in donor blood have been reported. In summary, the immediate decreases in blood lymphocyte counts and serum immunoglobulin concentrations are of slight to moderate degree and are without known adverse effects. Less information is available regarding long-term alterations of the immune system, and little data have been collected from prospective studies in which large numbers of donors have been thoroughly evaluated by modern techniques. In general, results of many laboratory studies have been altered. However, these abnormalities have been transient for the most part, and it has been difficult to document clinically significant adverse effects. Thus, the quantities of blood lymphocytes and plasma immunoglobulins that can be removed from healthy donors without causing significant immediate or long-term harm is unknown. Bearing these limitations in mind, the following recommendations are suggested regarding the frequency of repeated mechanical plasma-and-cytapheresis. 1) The usual requirements for whole blood donation must be met if the frequency of mechanical hemapheresis does not exceed once every eight weeks.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-term follow-up of donors cytapheresed more than 50 times

11 volunteers who had donated white blood cells or platelets more than 50 times over a 5- to 9-year period were studied to determine whether any adverse consequences of many cytaphereses could be detected. Among the donors no significant differences were found in 18 hematological and biochemical parameters when compared to a group of age- and sex-matched nondonor controls. Despite extensive cumulative lymphocyte losses sustained by these donors, the ratio of T, B, helper and suppressor cells has been maintained within the normal range. No detrimental effects of multiple cytapheresis on the donors' health has been demonstrated to date.

Adverse reactions to whole blood donation and plasmapheresis

Whole blood donation is recognized to be extremely safe, yet there have been reports of serious problems stemming from whole blood donation, and so-called "donor reactions" are regularly seen. While the physiologic causes of the common donor reactions are not completely understood, some effects of whole blood donation (such as transient iron deficiency) are understood but probably not significant. In order to avoid accepting any volunteer donor who might be at risk of a serious reaction, we may have been overly cautious in exclusion of potential donors. The pheresis donor is subjected to potential depletion of the protein or cellular elements being removed, problems caused by the device used for automated pheresis, or problems related to the infusion of potentially toxic substances. Documented benefit to the patient must balance these additional risks.