Differentiation of monocyte-derived dendritic cells under the influence of platelets

Interactions between platelets and the cancer immune microenvironment

Cancer is a leading cause of death in both China and developed countries due to its high incidence and low cure rate. Immune function is closely linked to the development and progression of tumors. Platelets, which are primarily known for their role in hemostasis, also play a crucial part in the spread and progression of tumors through their interaction with the immune microenvironment. The impact of platelets on tumor growth and metastasis depends on the type of cancer and treatment method used. This article provides an overview of the relationship between platelets and the immune microenvironment, highlighting how platelets can either protect or harm the immune response and cancer immune escape. We also explore the potential of available platelet-targeting strategies for tumor immunotherapy, as well as the promise of new platelet-targeted tumor therapy methods through further research.

Platelets interact with CD169+ macrophages and cDC1 and enhance liposome-induced CD8+ T cell responses

Historically platelets are mostly known for their crucial contribution to hemostasis, but there is growing understanding of their role in inflammation and immunity. The immunomodulatory role of platelets entails interaction with pathogens, but also with immune cells including macrophages and dendritic cells (DCs), to activate adaptive immune responses. In our previous work, we have demonstrated that splenic CD169+ macrophages scavenge liposomes and collaborate with conventional type 1 DCs (cDC1) to induce expansion of CD8+ T cells. Here, we show that platelets associate with liposomes and bind to DNGR-1/Clec9a and CD169/Siglec-1 receptors in vitro. In addition, platelets interacted with splenic CD169+ macrophages and cDC1 and further increased liposome internalization by cDC1. Most importantly, platelet depletion prior to liposomal immunization resulted in significantly diminished antigen-specific CD8+ T cell responses, but not germinal center B cell responses. Previously, complement C3 was shown to be essential for platelet-mediated CD8+ T cell activation during bacterial infection. However, after liposomal vaccination CD8+ T cell priming was not dependent on complement C3. While DCs from platelet-deficient mice exhibited unaltered maturation status, they did express lower levels of CCR7. In addition, in the absence of platelets, CCL5 plasma levels were significantly reduced. Overall, our findings demonstrate that platelets engage in a cross-talk with CD169+ macrophages and cDC1 and emphasize the importance of platelets in induction of CD8+ T cell responses in the context of liposomal vaccination.

Development of a Prediction Model for Short-Term Remission of Patients with Crohn's Disease Treated with Anti-TNF Drugs

Therapy with anti-tumor necrosis factor (TNF) has dramatically changed the natural history of Crohn's disease (CD). However, these drugs are not without adverse events, and up to 40% of patients could lose efficacy in the long term. We aimed to identify reliable markers of response to anti-TNF drugs in patients with CD. A consecutive cohort of 113 anti-TNF naive patients with CD was stratified according to clinical response as short-term remission (STR) or non-STR (NSTR) at 12 weeks of treatment. We compared the protein expression profiles of plasma samples in a subset of patients from both groups prior to anti-TNF therapy by SWATH proteomics. We identified 18 differentially expressed proteins (p ≤ 0.01, fold change ≥ 2.4) involved in the organization of the cytoskeleton and cell junction, hemostasis/platelet function, carbohydrate metabolism, and immune response as candidate biomarkers of STR. Among them, vinculin was one of the most deregulated proteins (p < 0.001), whose differential expression was confirmed by ELISA (p = 0.054). In the multivariate analysis, plasma vinculin levels along with basal CD Activity Index, corticosteroids induction, and bowel resection were factors predicting NSTR.

Inhibition of Dendritic Cell Activation and Modulation of T Cell Polarization by the Platelet Secretome

Platelet transfusions are a frequently administered therapy for especially hemato-oncological patients with thrombocytopenia. Next to their primary function in hemostasis, currently there is increased attention for the capacity of platelets to affect the function of various cells of the immune system. Here, we investigate the capacity of platelets to immuno-modulate monocyte-derived dendritic cells (moDC) as well as primary dendritic cells and effects on subsequent T cell responses. Platelets significantly inhibited pro-inflammatory (IL-12, IL-6, TNFα) and increased anti-inflammatory (IL-10) cytokine production of moDCs primed with toll-like receptor (TLR)-dependent and TLR-independent stimuli. Transwell assays and ultracentrifugation revealed that a soluble factor secreted by platelets, but not microvesicles, inhibited DC activation. Interestingly, platelet-derived soluble mediators also inhibited cytokine production by human ex vivo stimulated myeloid CD1c+ conventional DC2. Moreover, platelets and platelet-derived soluble mediators inhibited T cell priming and T helper differentiation toward an IFNγ+ Th1 phenotype by moDCs. Overall, these results show that platelets are able to inhibit the pro-inflammatory properties of DCs, and may even induce an anti-inflammatory DC phenotype, with decreased T cell priming capacity by the DC. The results of this study provide more insight in the potential role of platelets in immune modulation, especially in the context of platelet transfusions.

First comparative analysis concerning the plasma platelet contamination during MNC collection

BACKGROUND AND OBJECTIVES

Monocytes can be cultured into dendritic cells with addition of autologous plasma, which is highly prone to platelet contamination due to the apheresis process. Since platelets affect the maturation process of monocytes into dendritic cells and might even lead to a diminished harvest of dendritic cells, it is very important to reduce the platelet contamination. A new collection device (Spectra Optia) was analyzed, compared to two established devices (COM.TEC, Cobe Spectra) and evaluated regarding the potential generation of source plasma.

MATERIALS AND METHODS

Concurrent plasma collected during leukapheresis was analyzed for residual cell contamination in a prospective study with the new Spectra Optia apheresis device (n=24) and was compared with COM.TEC and Cobe Spectra data (retrospective analysis, n=72). Donor pre-donation counts of platelets were analyzed for their predictive value of contaminating PLTs in plasma harvests.

RESULTS

The newest apheresis device showed the lowest residual platelet count of the collected concurrent plasma (median 3.50×10⁹/l) independent of pre-donation counts. The other two devices and sets had a higher platelet contamination. The contamination of the plasma with leukocytes was very low (only 2.0% were higher than 0.5×10⁹/l).

CONCLUSIONS

This study showed a significant reduction of platelet contamination of the concurrent plasma collected with the new Spectra Optia device. This plasma product with low residual platelets and leukocytes might also be used as plasma for fractionation.

Leukapheresis in non-cytokine-stimulated donors with a new apheresis system: first-time collection results and evaluation of subsequent cryopreservation

BACKGROUND

Adoptive cell therapy based on mononuclear cells (MNCs) became an important modality of cancer immunotherapy. Data about collection results and donor response of leukapheresis with the Spectra Optia v.5.0 (Terumo BCT) in nonmobilized donors are required.

STUDY DESIGN AND METHODS

Twelve MNC collections were performed using the Spectra Optia v.5.0 in non-cytokine-stimulated donors. Leukapheresis products and peripheral blood samples from donors were assayed for CD45+, CD34+, CD3+, and CD14+ cells by flow cytometry. Prefreeze and postthaw cell counts, cell viability, and numbers of colony-forming units were assessed in cryobags and compared to data from cryovials.

RESULTS

Leukapheresis yielded a mean of 5.26×10(9) ±2.2×10(9) CD45+ cells, 1.5×10(9) ±0.77×10(9) CD14+ monocytes, and 2.28×10(9) ±1.2×10(9) CD3+ Tcells by processing 6690±930mL of whole blood. A significant positive correlation between yield of CD3+ Tcells and residual platelets (PLTs) and red blood cells (RBCs) was observed. This did not apply for CD34+ and CD14+ white blood cell subsets. Mean collection efficiencies for CD14+ monocytes and CD3+ Tcells were 61.8±17 and 37.2±18%, respectively. Recovery of CD14+ cells after cryopreservation was 75.2±8.2%, which was significantly lower than recovery of CD45+ cells (81.4±5.5%; p=0.01).

CONCLUSION

This study of a small cohort demonstrates that the Spectra Optia v.5.0 is capable of collecting low product volumes with satisfactory MNC yields and low residual RBCs and PLTs in non-cytokine-mobilized apheresis. Our data suggest that cryovials can serve as a representative surrogate for the primary product cryobag.

Role of platelets in neuroinflammation: a wide-angle perspective

OBJECTIVES

This review summarizes recent developments in platelet biology relevant to neuroinflammatory disorders. Multiple sclerosis (MS) is taken as the "Poster Child" of these disorders but the implications are wide. The role of platelets in inflammation is well appreciated in the cardiovascular and cancer research communities but appears to be relatively neglected in neurological research.

ORGANIZATION

After a brief introduction to platelets, topics covered include the matrix metalloproteinases, platelet chemokines, cytokines and growth factors, the recent finding of platelet PPAR receptors and Toll-like receptors, complement, bioactive lipids, and other agents/functions likely to be relevant in neuroinflammatory diseases. Each section cites literature linking the topic to areas of active research in MS or other disorders, including especially Alzheimer's disease.

CONCLUSION

The final section summarizes evidence of platelet involvement in MS. The general conclusion is that platelets may be key players in MS and related disorders, and warrant more attention in neurological research.

Innate immunity, coagulation and placenta-related adverse pregnancy outcomes

Maternal immunity undergoes subtle adjustment in order to tolerate the semi-allogeneic embryo and maintain the host defense against potential pathogens. Concomitantly, coagulation systems change from an anti-coagulant state to a pro-coagulant state to meet the hemostatic challenge of placentation and delivery. Innate immunity and blood coagulation systems are the first line of defense to protect a host against exogenous challenges, including alloantigens and mechanical insults, and preserve the integrity of an organism. The interactions between coagulation and immune systems have been extensively studied. Immune cells play a pivotal role in the initiation of the coagulation cascade, whereas coagulation proteases display substantial immuno-modulatory effects. Upon exogenous challenges, the immune and coagulation systems are capable of potentiating each other leading to a vicious cycle. Natural killer (NK) cells, macrophages (Mphis) and dendritic cells (DCs) are three major innate immune cells that have been demonstrated to play essential roles in early pregnancy. However, immune maladaptation and hemostatic imbalance have been suggested to be responsible for adverse pregnant outcomes, such as preeclampsia (PE), miscarriage, recurrent spontaneous abortion (RSA) and intrauterine growth restriction (IUGR). In this review, we will summarize the mutual regulation between blood coagulation and innate immune systems as well as their roles in the maintenance of normal pregnancy and in the pathogenesis of adverse pregnancy outcomes.