Recovery of white blood cells and platelets from leukoreduction system chambers of Trima Accel and COBE Spectra plateletpheresis devices

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.

Rapid generation of monocyte-derived antigen-presenting cells with dendritic cell-like properties

BACKGROUND

One of the major challenges in cellular therapy is the establishment and validation of simple and fast production protocols meeting good manufacturing practice (GMP) requirements. Dendritic cells (DCs) are of particular therapeutic interest, due to their critical role in T cell response initiation and regulation. Conventional wisdom states that DC generation from monocytes is a time-consuming protocol, taking up to 7-9 days.

STUDY DESIGN AND METHODS

This study systematically screened and validated numerous culture components and conditions to identify the minimal requirements, which can give rise to functional monocyte-derived antigen-presenting cells (MoAPCs) in less than 48 h (36 h MoAPC). A total of 36 h MoAPCs were evaluated in terms of surface marker expression, endocytic capability, and induction of antigen-specific T cell expansion via flow cytometry.

RESULTS

Screening of media compositions, glucose concentrations, and surface marker kinetics, particularly DC-SIGN as a DC-specific marker, allowed the generation of DC-like APCs in 36 h (36 h MoAPCs). A total of 36 h MoAPCs displayed a similar phenotype to 48 h MoAPC and standard 7 d MoDCs in terms of HLA-DP,DQ,DR, CD83, and DC-SIGN expression, while CD1a was preferentially expressed in standard MoDCs. Functional evaluation revealed that 36 h MoAPCs displayed reduced endocytosis capabilities and IL-12p70 production. However, 36 h MoAPCs were able to induce T cell expansion both in an allogenic and antigen-specific setting.

CONCLUSION

Our results indicate that mature 36 h MoAPCs possess DC-like capabilities by inducing antigen-specific T cell responses. This study has important implications for the generation of DC-based cellular therapies, allowing a more cost and time-efficient generation of APCs.

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.

Quantity, quality, and functionality of peripheral blood cells derived from residual blood of different apheresis kits

BACKGROUND

Research with primary human white blood cell (WBC) subpopulations requires high quantity, quality, and functionality of peripheral blood mononuclear cells (PBMCs) as a source to further characterize cellular subpopulations such as T and B lymphocytes, monocytes, or natural killer cells. Apart from buffy coats derived from whole blood, residual blood from preparative hemapheresis kits are used as a source for PBMCs, but knowledge on the yield and functionality of cells from different devices is limited.

STUDY DESIGN AND METHODS

We evaluated quantity and quality of PBMCs isolated from apheresis kits of two apheresis devices (AMICUS, Fenwal; and Trima Accel, Terumo BCT), the latter being our standard source for many years. PBMCs derived from Trima or AMICUS were tested for yield and subtype composition by flow cytometry. Functionality was assessed by cytokine induction of CD4⁺ and CD8⁺ T cells and by degranulation. Moreover, cytotoxic activity of natural killer cells was quantified by a real-time killing assay.

RESULTS

Mean numbers of isolated cells were 5.5 ± 2.4 × 10⁸ for AMICUS, and 10.3 ± 6.4 × 10⁸ for Trima Accel, respectively. The proportion of WBC subtypes corresponded to well-known numbers from whole blood, with minor differences between the two apheresis systems. Likewise, minor differences in cytokine induction were found in stimulated CD4⁺ or CD8⁺ T cells. Finally, PBMCs derived from the two systems showed comparable cytotoxic activity.

CONCLUSION

PBMC derived from residual blood of the AMICUS and Trima Accel apheresis devices serve as an economic and easily accessible source for functional PBMCs with comparable quantity and quality to PBMCs derived from whole blood.

Combined cytotoxic activity of an infectious, but non-replicative herpes simplex virus type 1 and plasmacytoid dendritic cells against tumour cells

Malignant melanoma is an aggressive tumour of the skin with increasing incidence, frequent metastasis and poor prognosis. At the same time, it is an immunogenic type of cancer with spontaneous regressions. Most recently, the tumoricidal effect of plasmacytoid dendritic cells (pDC) and their capacity to overcome the immunosuppressive tumour microenvironment are being investigated. In this respect, we studied the effect of the infectious, but replication-deficient, herpes simplex virus 1 (HSV-1) d106S vaccine strain, which lacks essential immediate early genes, in pDC co-cultures with 11 melanoma cell lines. We observed a strong cytotoxic activity, inducing apoptotic and necrotic cell death in most melanoma cell lines. The cytotoxic activity of HSV-1 d106S plus pDC was comparable to the levels of cytotoxicity induced by natural killer cells, but required only a fraction of cells with effector : target ratios of 1 : 20 (P < 0·05). The suppressive activity of cell-free supernatants derived from virus-stimulated pDC was significantly neutralized using antibodies against the interferon-α receptor (P < 0·05). In addition to type I interferons, TRAIL and granzyme B contributed to the inhibitory effect of HSV-1 d106S plus pDC to a minor extent. UV-irradiated viral stocks were significantly less active than infectious particles, both in the absence and presence of pDC (P < 0·05), indicating that residual activity of HSV-1 d106S is a major component and sensitizes the tumour cells to interferon-producing pDC. Three leukaemic cell lines were also susceptible to this treatment, suggesting a general anti-tumour effect. In conclusion, the potential of HSV-1 d106S for therapeutic vaccination should be further evaluated in patients suffering from different malignancies.

Leukoreduction system chambers are an efficient, valid, and economic source of functional monocyte-derived dendritic cells and lymphocytes

The demand for human monocyte-derived dendritic cells (moDCs), as well as for primary human B and T lymphocytes for immunological research purposes has been increased in recent years. Classically, these monocytes are isolated from blood, leukapheresis products or buffy coats of healthy donors by plastic adherence of peripheral blood mononuclear cells (PBMCs), followed by stimulation with granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, while lymphocytes are usually isolated from the non-adherent fraction (NAF) by magnetic cell sorting. However, donor-blood is a limited resource and not every blood bank offers leukapheresis products or buffy coats for laboratory use. Additionally, a leukapheresis is very expensive and also the generation/isolation of cells is time- and cost-intensive. To overcome some of these obstacles, we evaluated if low-cost leukoreduction system chambers (LRSCs), which arise after routine donor plateletpheresis procedures, and are usually discarded, would be an alternative and appropriate source of PBMCs to generate moDCs and to isolate lymphocytes. By analyzing the number and phenotype of immature and mature dendritic cells (DCs), as well as of B and T lymphocytes derived from LRSCs, we found all cells to be of high quantity and quality. Further investigations on DCs comprising transwell migration assays, allogeneic mixed lymphocyte reactions (MLR), cytokine secretion assays, and cytotoxic T cell induction assays revealed high migratory, as well as stimulatory capacity of these cells. In addition, DCs and T cells were efficiently electroporated with mRNA and showed characteristic cytokine production after co-culture, demonstrating LRSCs as an efficient, valid, and economic source for generation of moDCs and lymphocytes for research purposes.

Storage induced apoptosis of peripheral blood mononuclear cells obtained from leucoreduction system chambers

BACKGROUND AND OBJECTIVES

Recently, it was reported that leucocytes obtained from leucoreduction system chambers (LRSCs) after plateletapheresis show excellent quality due to culture of dendritic cells. This study analysed apoptosis of mononuclear cells derived from LRSCs of single platelet units (SPUs) and double platelet units (DPUs) during storage.

MATERIALS AND METHODS

This randomized prospective study compared eighteen single and double platelet units produced with the Trima Accel cell separator. Buffy coat was drained from the LRSCs and analysed after 1, 6, 24, 48 and 72 h. CD45+ lymphocytes and CD14+ monocytes cells as well as Annexin-V+ and 7-AAD+ mononuclear cells were measured by flow cytometry.

RESULTS

The WBC concentration of LRSCs obtained from SPUs and DPUs differed significantly (SPUs: 0·93 ± 0·32 ×10(5) per μl WBCs; DPUs: 1·71 ± 0·55 ×10(5) per μl WBCs; P<0·001). Processed blood volume (PBV) correlated significantly with WBC concentration (r(2)=0·75, P<0·001). Fifty percent of monocytes were Annexin-V-positive 1 h after production decreasing to 30% during 24 h of storage. Compared to that, the part of late apoptotic or necrotic PBMCs increased later on, after 24 h. After 24 h, Annexin-V- and 7-AAD-positive, late apoptotic and necrotic lymphocytes and monocytes doubled.

CONCLUSION

PBMCs stored in autologous plasma in PVC-bags at room temperature did not show an increase of 7-AAD-positive PBMCs during 24 h prior to cell processing but increased significantly thereafter.