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

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.

Long-term persistent lymphopenia in hematopoietic stem cell donors after donation for donor lymphocyte infusion

OBJECTIVES

To analyze the consequences of lymphocyte donations on lymphopoiesis in donors having previously undergone hematopoietic stem cell collection for allogeneic stem cell transplantation.

METHODS

Repeated analysis of leukocyte subsets in the peripheral blood of 76 hematopoietic stem cell donors undergoing lymphocyte donation(s) for DLI.

RESULTS

Grade I/II lymphopenia was present in 22 donors (29%) just before first apheresis for lymphocyte collection, demonstrating that former stem cell donation induced prolonged lymphopenia in a subset of donors. The monocytic lineage was not affected. Older age and history of PBSC harvest constituted 2 independent factors of lymphopenia, but had no influence on monocytopenia. The first apheresis induced lymphopenia in 36 donors (47%) and monocytopenia in 23 donors (39%). Lymphopenia before first apheresis and prior history of PBSC harvest were independent factors of apheresis-induced lymphopenia while those factors had no influence on monocytopenia. A time-dependent decrease in lymphocyte counts was observed in donors undergoing repeated aphereses, resulting in persistent and prolonged lymphopenia in 50% of donors. No persistent monocytopenia over time and aphereses was observed. Kaplan-Meier estimate of the risk to develop persistent lymphopenia after multiple aphereses was 21% +/- 6% at 2 months, 38% +/- 8% at 4 months, and 64% +/- 10% at 12 months. After Cox regression analysis, previous PBSC harvest remained the unique factor associated with the risk for persistent lymphopenia.

CONCLUSIONS

Monitoring the potential long-term effects of repeated aphereses in hematopoietic stem cell donors appears important. Selecting young bone marrow donors for subsequent DLI significantly reduces the risk for acute and prolonged lymphopenias.

Sustained decreases in platelet count associated with multiple, regular plateletpheresis donations

BACKGROUND

Transient but significant decreases in platelet counts have been documented to occur in donors undergoing single and serial short-term plateletpheresis collections. The effect of long-term regular plateletpheresis on donor platelet counts has not been characterized.

STUDY DESIGN AND METHODS

A retrospective study was performed to evaluate the effects of long-term regular plateletpheresis donation on donor platelet counts. A computerized database containing records of 11,464 apheresis collections from 939 donors over a 4-year period was queried for serial preapheresis platelet counts. Donors were categorized by sex, age, and cumulative number of donations. The average difference in platelet counts (mDeltaPC) between each donor's first and last platelet count during this period was calculated for each category. A subgroup of frequent donors was selected for analysis of mDeltaPC, using the baseline platelet count obtained before the first plateletpheresis procedure.

RESULTS

A significant and sustained decrease in platelet count was identified for all donation frequency categories. The frequency of donation correlated directly with decrease in platelet count for all but the highest-frequency donation group, in which deferrals for low platelet count blunted the extent of the mDeltaPC. A mean decrease of 40,000 per microL from baseline occurred in the frequent-donor subgroup. A total of 84 donors (9%) were deferred for low platelet count. The majority returned to donate successfully after temporary deferral.

CONCLUSIONS

Regular plateletpheresis donors develop sustained decreases in platelet count. However, clinically significant thrombocytopenia is unusual when rigorous ongoing review and prudent deferral policies are established and followed.

Quality evaluation of plateletpheresis using the new AMICUS (Baxter) cell separator: evolution of CD 62 expression

The purpose of this study was to evaluate the new AMICUS (Baxter-Fenwal Division) cell separator in terms of donor safety, efficiency, and quality of the product obtained. One hundred eighty-three single-donor plateletpheresis procedures were performed, using a collection of 4-4.5 x 10(11) platelets as endpoint. During the first part of the study, the mean volume processed was 3,225 ml and the mean procedure duration 69.5 min. During the second part, after a software change, the mean volume and mean procedure time were 3,071 ml and 68.3 min, respectively. According to local policy, every collection bag was separated into two therapeutic units each containing a mean of 1.87 (1.83) x 10(11) platelets. The white blood cell (WBC) contamination per therapeutic unit was less than 5 x 10(6) in 91% of phereses performed in part one of the study and in 98% of phereses performed in part two. During the recommended 5 days storage, sequential in vitro analyses were performed in 27 units, showing limited platelet activation according to CD62 expression and morphological changes on electron microscopy (EM). Furthermore, there was a correlation between CD62 expression and the degree of WBC contamination (P = 0.03). In conclusion, platelet collection with the new Amicus allows for high platelet yields of adequate quality as judged by WBC content, CD62 expression, and electron microscopic morphological changes.

Donor lymphocyte infusion for the treatment of relapse after allogeneic hematopoietic stem cell transplantation

The results of donor lymphocyte infusion (DLI) for treatment of relapse after bone marrow transplantation (BMT) are reviewed. Durable complete remission can be achieved at the molecular level for a majority (more than 70%) of patients with CML, when treated at early relapse. Results are less favourable for acute leukemias, although useful responses have been reported. Data are scarce though promising for myelodysplastic syndromes and multiple myeloma. Major treatment-associated toxicities are GVHD and bone marrow aplasia. The latter complication can be predicted by evaluating the level of residual donor-derived hematopoiesis. Modification of infused cells (CD8 negative selection or transduction with a suicide gene), addition of peripheral blood stem cells, and early implementation of escalating doses may counteract the complications and increase the response rate. Response rate is variably influenced by the presence of chronic GVHD after initial BMT, T-cell depleted BMT, underlying disease and stage at relapse, and the level of mixed chimerism. DLI is a direct demonstration of the graft-versus-leukemia effect (GVL). Because GVL after BMT is sometimes the predominant cause of cure, it may be advisable in such situations to redirect the conditioning regimens for BMT towards engraftment and less immediate cytotoxicity.

The role of flow cytometry in improving biocompatibility in transfusion medicine

In transfusion medicine, blood and blood components, donors and patients are increasingly confronted with biomaterials. The need to understand the response of human blood to contact with these artificial surfaces has led to multiple studies on the biocompatibility of biomaterials. Up to this time, these investigations have predominantly been performed using physical, immunological and biochemical methods. Many of these approaches are useful in investigating the multiple factors involved in blood-biomaterial interactions. However, they always reflect the overall behaviour of whole cellular populations in local or systemic reactions. The application of multiparameter flow cytometry, on the other hand, provides insight into antigenic expression and changes at the single-cell level. Therefore, the technique of flow cytometry represents a new and powerful way of analysing and improving the biocompatibility of these materials in blood-contacting applications in this field.

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.

Iron Deficiency Developing in Patients with Homozygous Hypercholesterolaemia on Long-term Plasmapheresis is Significantly Contributed to by Extracorporeal Haemolysis

Patients with homozygous hypeicholesterolaemia are notoriously refractory to pharmacologic intervention, leaving regular long-term plasmapheresis as one of the most effective forms of therapy. In this situation we noted the universal development of anaemia; accordingly, its pathogenesis was investigated in a stable cohort of patients over a two year period. Radionuclide studies were carried out in 8 of the 9 available individuals: of these 3 who were not on treatment and 3 out of 5 on the apheresis programme had mean red cell lifespan below the lower level of our normal range. The creation of an arterio-venous fistula and subsequent performance of plasma exchange procedures every two weeks was followed by a falling haemoglobin concentration and the appearance of hypochromasia and microcytosis. The latter was the result of substantial loss of iron through venesection, in the discard plasma and by a transient peak of the iron in the urine: the last two compartments were studied using inductively coupled plasma atomic emission spectrometry (ICP-AES). Such depletion could not be compensated for by a dietary intake of iron that barely met the recommended daily allowance whereas the anaemia reversed readily on oral supplementation. This is the first report of extracorporeal haemolysis in this clinical setting and recognition of its pathophysiology directly influences management. Thus, oral iron supplementation should prevent anaemia and its symptoms whilst also circumventing the paradoxical hyperviscosity that might otherwise occur from iron deficiency.

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.

Collection of peripheral blood mononuclear cells as a byproduct of plateletpheresis with two different blood cell separators

Peripheral blood mononuclear cells (PBMC) were collected as a byproduct of plateletpheresis of normal blood cell donors using modifications to standard automated protocols on either the CS-3000 or Spectra blood cell separator machine. Comparison of the PBMC products obtained showed X +/- SD WBC yields of 5.3 +/- 3.4 vs. 3.8 +/- 2.0 x 10(9) with the CS-3000 and Spectra, respectively (P < .0001). The majority of the cells were lymphocytes, with 13-15% monocytes with both machines. Sixteen percent of the WBC collected with the Spectra, but only 1% of those collected with the CS-3000, were granulocytes. The CS-3000 PBMC product contained fewer RBC (0.2 +/- 0.1 x 10(11) vs. 2.4 +/- 0.6 x 10(11)) and more platelets (1.6 +/- 0.6 x 10(11) vs. 0.35 +/- 0.39 x 10(11)) in a smaller volume (40 +/- 14 ml vs. 229 +/- 37 ml) than the Spectra products. Comparison of the platelet collections harvested when PBMC were also collected to platelets harvested using standard procedures on the same machine showed no change in platelet, WBC, or RBC yields for the Spectra. A significant increase in mean WBC contamination from 40 +/- 56 x 10(7) to 112 +/- 205 x 10(7) and a small, but statistically insignificant, decrease in platelet yield from 4.1 +/- 1.2 x 10(11) to 3.9 +/- 1.8 x 10(11) was observed in the CS-3000 platelet collections when PBMC were harvested. There was no sustained change in donor lymphocyte counts and no change in acute donor side effects or time requirements when PBMC were collected.(ABSTRACT TRUNCATED AT 250 WORDS)