Effect of peripheral blood mononuclear cell cryopreservation on innate and adaptive immune responses

Reduced monocytic IL10 expression in PD1 inhibitor-treated patients is a harbinger of severe immune-related adverse events

BACKGROUND

Despite remarkable clinical efficacy, little is known about the system-wide immunological alterations provoked by PD1 blockade. Dynamics of quantitative immune composition and functional repertoire during PD1 blockade could delineate cohort-specific patterns of treatment response and therapy-induced toxicity.

METHODS

We longitudinally assessed therapy-induced effects on the immune system in fresh whole blood using flow cytometry-based cell quantifications, accompanied by analyses of effector properties of all major immune populations upon cell-type specific stimulations. 43 cancer patients undergoing PD1 blockade were recruited with assessments performed pre-treatment and before cycles 2/4/6, which resulted in the collection of more than 30,000 cytometric data values.

RESULTS

We observed no intrinsic immune pattern correlating with clinical outcome before PD1 blockade initiation, but cohort-specific immune alterations emerged during therapy. The most striking evolving changes in therapy responders were an increase in activated T and NK cell subsets, which showed high IFNγ and TNFα expression upon ex vivo stimulation. Patients affected by severe immune-related adverse events (s-irAE) presented with an analogously increased number of activated CD4 + and CD8 + T cells compared to patients with no/mild irAE, but lacked the functional divergences observed between responders versus non-responders. Instead, their monocytes showed discriminatory functional deficits with less IL10 production upon stimulation, which led to an abrogated inhibition of T cell proliferation in vitro and thus may account for the observed T cell expansion in patients with s-irAE.

CONCLUSION

Our holistic explorative approach allowed the delineation of clinically relevant cohorts by treatment-triggered immune changes, potentially enabling better patient stratification and further revealed new mechanistic insights into the pathogenesis of s-irAE.

The Effect of Cryopreservation on T-Cell Subsets by Flow Cytometry Automated Algorithmic Analysis and Conventional Analysis

BACKGROUND

Low-temperature cryopreservation is a common method for scientific research and clinical sample preservation when utilizing flow cytometry. In flow cytometry data analysis, traditional manual "gating" is susceptible to past experience and faces the challenge of manual subjective bias, time-consuming, and multidimensional data analysis. With the development of algorithms, the advantages of dimensionality reduction and clustering in result analysis are gradually becoming more prominent.

METHODS

Flow cytometry was used to detect the effects of cryopreservation and freeze-thaw cycle on T-cell subsets, and to analyze the data using automated algorithmic analysis and conventional manual "gating" methods.

RESULTS

The results showed that the number and viability of cells decreased slightly after one freeze-thaw within 2 weeks of cryopreservation, and there was no significant change in the subpopulation proportions and spatial locations by both analysis methods. The changes were significant with the increase of cryopreservation time and freeze-thaw cycle, which may be due to changes in the molecular conformation of the maker as a result of cryopreservation.

CONCLUSION

The results indicate that both analysis methods have reached similar conclusions, but the repeatability and objectivity of automated algorithmic analysis have compensated for the uncertainty brought about by the subjective discretization of traditional manual "gating." In addition, the automated algorithmic analysis more intuitively highlights the spatial positional variations in the relationships between cell populations.

The impact of cryopreservation on cytokine secretion and polyfunctionality in human PBMCs: a comparative study

Introduction

Human peripheral blood mononuclear cells (hPBMCs) are widely used in fundamental research and clinical applications as studying their responses to in vitro activation is an effective way to uncover functional alterations and disease associated phenotypes. However, the availability of samples in large numbers at a specific time and location remains challenging, hence they often might preferably be collected and cryopreserved for later analysis. While the effect of cryopreservation on viability and cell surface expression is well established, changes in activity and cytokine secretion still lead to conflicting results as it is often measured in bulk or within the cells.

Methods

Here, we used our platform for dynamic single-cell multiplexed cytokine secretion measurement and compared it to a traditional intracellular cytokine staining to quantify the effect of cryopreservation on cytokine secretion and expression of individual hPBMCs.

Results

Following stimulation with LPS or anti-CD3/CD28 antibodies for up to 36 or 72 h incubation, we observed distinct alterations in cytokine responses due to cryopreservation when comparing to fresh samples, but also remarkable consistencies for some cytokines and parameters. In short, the frequencies of cytokine-secreting cells in cryopreserved samples were lower for IL-6 (LPS), IL1-β (CD3/CD28) and IFN-γ (CD3/CD28), while the frequency and dynamics of IL-8 secretion were strongly impacted in all cases. We observed a large disconnect between cytokine expression and secretion for TNF-α, where the expression dramatically increased after cryopreservation, but actual secretion was, in comparison, remarkably stable. The polyfunctionality of single cells was altered by cryopreservation in specific co-secreting populations led by the effects on IL-6 or IL-8 secretion. Among immune cells, cryopreservation seemed to affect lymphocytes and monocytes differently as effects appeared early on in lymphocytes while generally observed in later time points in monocytes.

Conclusion

Together, this study offers an in-depth quantitative insight into the biological behavior of immune cells in response to cryopreservation and stimulation, further providing some insights into conflicting results in the literature as well as guidelines for researchers planning to assess cytokine-secreting from frozen hPBMCs in immunological research or clinical applications.

Cellular response of advanced triple cultures of human osteocytes, osteoblasts and osteoclasts to high sulfated hyaluronan (sHA3)

Bone remodelling, important for homeostasis and regeneration involves the controlled action of osteoblasts, osteocytes and osteoclasts. The present study established a three-dimensional human in vitro bone model as triple culture with simultaneously differentiating osteocytes and osteoclasts, in the presence of osteoblasts. Since high sulfated hyaluronan (sHA3) was reported as a biomaterial to enhance osteogenesis as well as to dampen osteoclastogenesis, the triple culture was exposed to sHA3 to investigate cellular responses compared to the respective bone cell monocultures. Osteoclast formation and marker expression was stimulated by sHA3 only in triple culture. Osteoprotegerin (OPG) gene expression and protein secretion, but not receptor activator of NF-κB ligand (RANKL) or sclerostin (SOST), were strongly enhanced, suggesting an important role of sHA3 itself in osteoclastogenesis with other targets than indirect modulation of the RANKL/OPG ratio. Furthermore, sHA3 upregulated osteocalcin (BGLAP) in osteocytes and osteoblasts in triple culture, while alkaline phosphatase (ALP) was downregulated.

Differential anti-viral response to respiratory syncytial virus A in preterm and term infants

BACKGROUND

Preterm infants are more likely to experience severe respiratory syncytial virus (RSV) disease compared to term infants. The reasons for this are multi-factorial, however their immature immune system is believed to be a major contributing factor.

METHODS

We collected cord blood from 25 preterm (gestational age 30.4-34.1 weeks) and 25 term infants (gestation age 37-40 weeks) and compared the response of cord blood mononuclear cells (CBMCs) to RSVA and RSVB stimulation using neutralising assays, high-dimensional flow cytometry, multiplex cytokine assays and RNA-sequencing.

FINDINGS

We found that preterm and term infants had similar maternally derived neutralising antibody titres to RSVA and RSVB. Preterm infants had significantly higher myeloid dendritic cells (mDC) RSV infection compared to term infants. Differential gene expression analysis of RSVA stimulated CBMCs revealed enrichment of genes involved in cytokine production and immune regulatory pathways involving IL-10, IL-36γ, CXCL1, CXCL2, SOCS1 and SOCS3 in term infants, while differentially expressed genes (DEGs) in preterm infants were related to cell cycle (CDK1, TTK, ESCO2, KNL1, CDC25A, MAD2L1) without associated expression of immune response genes. Furthermore, enriched genes in term infants were highly correlated suggesting an increased co-ordination of their immune response to RSVA. When comparing DEGs in preterm and term infants following RSVB stimulation, no differences in immune response genes were identified.

INTERPRETATION

Overall, our data suggests that preterm infants have a more restricted immunological response to RSVA compared with term infants. While further studies are required, these findings may help to explain why preterm infants are more susceptible to severe RSV disease and identify potential therapeutic targets to protect these vulnerable infants.

FUNDING

Murdoch Children's Research Institute Infection and Immunity theme grant.

Quantifying the Detrimental Effects of Multiple Freeze/Thaw Cycles on Primary Human Lymphocyte Survival and Function

The use of cryopreserved peripheral blood mononuclear cells is common in biological research. It is widely accepted that primary cells are rendered unusable by several freezing cycles, although this practice might be very helpful when the biological material is valuable and its re-collection is impractical. To determine the extent to which primary cells undergoing repeated freezing cycles are comparable to one another and to fresh samples, we evaluated overall lymphocyte viability, their proliferation and cytokine production capabilities, as well as the levels of 27 cell subtypes in ten human peripheral blood mononuclear cells frozen for five years and repeatedly thawed. As expected, we observed a progressive increase in cell death percentages on three rounds of thawing, but the frequency of the main lymphocyte subsets was stable across the three thawings. Nevertheless, we observed a significant reduction of B cell frequency in frozen samples compared to fresh ones. On repeated thawings and subsequent conventional stimulation, lymphocyte proliferation significantly decreased, and IL-10, IL-6, GM-CSF, IFN-gamma, and IL-8 showed a trend to lower values.

Comparative flow cytometry-based immunophenotyping analysis of peripheral blood leukocytes before and after fixation with paraformaldehyde

Flow cytometry based immunophenotyping provides prime insight into cellular population composition and characteristics, and is widely used in basic and clinical research. Challenges in processing peripheral blood samples in a timely manner necessitate protocol adaptations and utilization of fixatives. Fixation, however, may introduce artifacts to the flow cytometry readout. We performed a comparative flow cytometry immunophenotyping analysis of 13 immune cell populations in the whole blood using a staining protocol with and without fixation step. Freshly procured human peripheral blood samples were stained with a panel of 33 fluorochrome-conjugated antibodies. Samples were processed using a protocol with or without a paraformaldehyde-based fixation step, and matching sample pairs were analyzed by flow cytometry. Our results show that paraformaldehyde-based fixation, in comparison to matched unfixed samples, did not significantly affect population distribution and frequency for: B cells, Plasmablasts, Dendritic cells, NK cells, Granulocytes, Neutrophils, Eosinophils, or Hematopoietic Stem/Progenitor Cells. However, fixation led to significant marker shifts in the subpopulation distribution in CD4, T regulatory, CD8, Monocytes, and Basophils. These results indicate the importance of pre-experimental assessment of fixation-introduced artifacts in the flow cytometry output when considering the feasibility of fresh processing. This is especially important for samples analyzed using comprehensive exploratory immunoprofiling panels.

Generation of effector Vγ9Vδ2 T cells and evaluation of their response to phosphoantigen-loaded cells

Vγ9Vδ2 T cells are non-canonical T cells that use their T cell receptor to detect phosphoantigens bound to the internal domain of the HMBPP receptor (butyrophilin 3/2A1 complex). This protocol describes the expansion and purification of human effector Vγ9Vδ2 T cells from human buffy coat and describes how to assess their activation by antigen-containing target cells. While specifically focused on cytokine production, this protocol can be readily adapted to evaluate other effector functions of activated Vγ9Vδ2 T cells. For complete details on the use and execution of this protocol, please refer to Hsiao et al. (2022) and Hsiao and Wiemer (2018).

Comprehensive evaluation of the effects of long-term cryopreservation on peripheral blood mononuclear cells using flow cytometry

Human peripheral blood mononuclear cells (PBMCs) originate from hematopoietic stem cells in the bone marrow, which mainly includes lymphocytes (T cells, B cells, and natural killer cells) and monocytes. Cryopreserved PBMCs providing biobank resources are crucial for clinical application or scientific research. Here, we used flow cytometry to explore the influence of long-term cryopreservation on the quality of PBMCs with the aim of providing important evidence for the effective utilization of biobank resources. The PBMCs were isolated from the peripheral blood, which was collected from volunteers in the hospital. After long-term cryopreservation in liquid nitrogen, we analyzed the changes in cell numbers, viability, and multiple subtypes of PBMCs and studied the apoptosis, proliferation, activation, function, and status of T cells in comparison with freshly isolated PBMCs by flow cytometry, and then further tracked the effects of long-term cryopreservation on the same sample. Although the different cell types in the PBMCs dynamically changed compared with those in the freshly isolated samples, PBMC recovery and viability remained stable after long-term cryopreservation, and the number of most innate immune cells (e.g., monocytes and B cells) was significantly reduced compared to that of the freshly isolated PBMCs or long-term cryopreserved PBMCs; more importantly, the proportion of T cell subtypes, apoptosis, proliferation, and functional T cells, except for Tregs, were not affected by long-term cryopreservation. However, the proportions of activated T, naïve T, central memory T, effector T, and effector memory T cells dynamically changed after long-term cryopreservation. This article provides important evidence for the effective utilization of biobank resources. Long-term cryopreserved PBMCs can be partly used as biological resources for clinical research or basic studies, but the effect of cryopreservation on PBMCs should be considered when selecting cell samples, especially in research relating to activating or inhibiting function.

Quantitative and Functional Assessment of the Influence of Routinely Used Cryopreservation Media on Mononuclear Leukocytes for Medical Research

Quantitative and functional analysis of mononuclear leukocyte populations is an invaluable tool to understand the role of the immune system in the pathogenesis of a disease. Cryopreservation of mononuclear cells (MNCs) is routinely used to guarantee similar experimental conditions. Immune cells react differently to cryopreservation, and populations and functions of immune cells change during the process of freeze–thawing. To allow for a setup that preserves cell number and function optimally, we tested four different cryopreservation media. MNCs from 15 human individuals were analyzed. Before freezing and after thawing, the distribution of leukocytes was quantified by flow cytometry. Cultured cells were stimulated using lipopolysaccharide, and their immune response was quantified by flow cytometry, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA). Ultimately, the performance of the cryopreservation media was ranked. Cell recovery and viability were different between the media. Cryopreservation led to changes in the relative number of monocytes, T cells, B cells, and their subsets. The inflammatory response of MNCs was altered by cryopreservation, enhancing the basal production of inflammatory cytokines. Different cryopreservation media induce biases, which needs to be considered when designing a study relying on cryopreservation. Here, we provide an overview of four different cryopreservation media for choosing the optimal medium for a specific task.

Characteristics of Biotin lipoyl attachment and 2-oxoacid dehydrogenase acyltransferase of the parasitic nematode Haemonchus contortus and its modulatory functions on goat PBMCs in vitro

Biotin lipoyl attachment and 2-oxoacid dehydrogenase acyltransferase (BLAODA), as an essential excretion of Haemonchus contortus (HcESPs), was identified to have antigenic functions. T helper-9 (Th9) cells secrete interleukin (IL)-9, a signature cytokine associated with tumour immunology, allergy and autoimmunity. Nonetheless, the understanding of modulatory functions of BLAODA on Th9 and other immune cells is limited. In this study, the BLAODA gene was cloned, and the recombinant (r) protein of BLAODA (rHcBLAODA) was expressed and immunoblotting was performed. The results revealed that HcBLAODA gene was successfully cloned and rHcBLAODA protein was expressed. The localization of rHcBLAODA was confirmed on the surface of gut sections from adult H. contortus. The rHcBLAODA protein capability to react precisely with anti-H. contortus antibodies were confirmed by immunoblotting and immunofluorescence assay (IFA). Further functional analysis showed that interaction of rHcBLAODA with host cells significantly enhanced Th9 cells generation, IL-9 expression, nitric oxide production and cell apoptosis while suppressing the cells proliferation and cells migration depending on the concentration. Overall, these findings suggest that rHcBLAODA protein could modulate the host immune response by inducing Th9 cells to secrete IL-9 cytokine in vitro.

The Escalation of Osteosarcoma Stem Cells Apoptosis After the Co-Cultivation of Peripheral Blood Mononuclear Cells Sensitized with Mesenchymal Stem Cells Secretome and Colony Stimulating Factor-2 in vitro

Introduction

Peripheral blood mononuclear cells (PBMCs) sensitized with mesenchymal stem cells (MSCs) secretome and/or colony stimulating factor-2 (CSF-2) as an immunotherapy candidate may escalate osteosarcoma stem cells (OS-SCs) apoptosis. This study aimed to investigate the escalation of osteosarcoma stem cells’ apoptosis after the co-cultivation with PBMCs sensitized by MSCs secretome with/or CSF-2 and it was completed by analyzing the level of serum tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) and tumor necrosis factor-α (TNF-α) level, annexin V binding, caspase-3 and caspase-8 expression in vitro.

Methods

OS-SCs were derived from a single human osteosarcoma sample with its high grade and osteoblastic essential clinical characteristics obtained from a biopsy before the chemotherapy treatment. They were then isolated and cultured confirmed by the cluster of differentiation-133 (FITC) by applying immunofluorescence analysis with fluorescein isothiocyanate (FITC) labeled. MSCs secretome was obtained with cells extracted from the bone marrow of a healthy patient. Furthermore, enzyme linked immunosorbent assay (ELISA) was utilized to analyze sTRAIL and TNF-α level in each group. The expression of caspase-3, caspase-8, and annexin V assay in each group was examined by applying the immunofluorescence labeled with FITC. The comparison analysis between treatment groups and the control group was performed by utilizing the analysis of variance (ANOVA) and continued with Tukey Honest Significant Difference (HSD) (p<0.05).

Results

There was a significant difference in the upregulation of sTRAIL and TNF-α level indicated by the increased annexin V, caspase-3, and caspase-8 expression binding between groups (p<0.05).

Conclusion

MSCs Secretome and CSF-2 could significantly increase the activity of PBMCs through the improvement of sTRAIL and TNF-α levels which could lead to the escalation of OS-SCs apoptosis through an enhanced expression of caspase 3, caspase 8 and annexin V binding in vitro.

In Vitro Characterization of the Innate Immune Pathways Engaged by Live and Inactivated Tick-Borne Encephalitis Virus

Tick-borne encephalitis virus (TBEV) infection can lead to inflammation of the central nervous system. The disease can be effectively prevented by whole inactivated virus vaccines. Here, we investigated the innate immune profile induced in vitro by the antigen component of the vaccines, inactivated TBEV (I-TBEV), to gain insights into the mechanism of action of the TBE vaccine as compared to the live virus. To this end, we exposed human peripheral blood mononuclear cells (PBMCs) to inactivated and live TBEV and assessed cellular responses by RNA sequencing. Both inactivated and live TBEV significantly induced an interferon-dominated gene signature and an increased RIG-I-like receptor (RLR) expression. Using pathway-specific inhibitors, we assessed the involvement of pattern recognition receptors in the sensing of inactivated or live TBEV. Only RLR pathway inhibition significantly suppressed the downstream cascade induced by I-TBEV, while responses to the replicating virus were impacted by the inhibition of RIG-I-like, as well as Toll-like, receptors. Our results show that inactivated and live TBEV predominantly engaged an interferon response in our in vitro PBMC platform, and indicate RLRs as the main pattern recognition receptors involved in I-TBEV sensing.

Effects of long-term cryopreservation of PBMC on recovery of B cell subpopulations

Cryopreservation of human peripheral blood mononuclear cells (PBMC) is used in many clinical and research applications to avoid direct and on-site analysis of samples. Storage of PBMC further allows prequalification of donor cells for routine laboratory methods involving the evaluation of immune responses. Previous studies reported changes in cellular composition and phenotype of PBMC following the freezing procedure. In our 12-month follow-up study, we focused on B cells and proportional representation of B cell subpopulations during long-term storage at -80 °C. Over the 12-month period, we observed a gradual decline in B cell viability and recovery. Notably, no changes in the proportional representation of human B cell subpopulations occurred in this period and the functional response elicited by antigen and TLR9 ligand CpG remained comparable to that observed after short-term storage for one month.