Project description:The Mixed Lymphocyte Reaction (MLR) consists in the allogenic co-culture of monocytes derived dendritic cells (MoDCs) with T cells from another donor. This in vitro assay is largely used for the assessment of immunotherapy compounds. Nevertheless, the phenotypic changes associated with lymphocyte responsiveness under MLR have never been thoroughly evaluated. Here, we used multiplex cytokine and chemokine assays, multiparametric flow cytometry and single cell RNA-sequencing to deeply characterize T cells activation and function in the context of CD4+- and CD8+-specific MLR kinetics. We showed that CD4+ and CD8+ T cells in MLR share common classical markers of response such as polyfunctionality, increased proliferation and CD25 expression but differ in their kinetics and amplitude of activation as well as their patterns of cytokines secretion and immune checkpoints expression. The analysis of immunoreactive KI67+CD25+ T cells identified PBK, LRR1 and MYO1G as new potential biomarkers of MLR response. Using cell-cell communication network inference and pathway analysis on single cell RNA-sequencing data, we also highlighted key components of the immunological synapse occurring between T cells and the stimulatory MoDCs together with downstream signaling pathways involved in CD4+ and CD8+ T cells activation. These results provide a deep understanding of the kinetics of the MLR assay for CD4+ or CD8+ T cells and may allow to identify new strategies for immunotherapy in cancer.
Project description:Characterization of CD4+ and CD8+ T cells responses in the Mixed Lymphocyte Reaction by flow cytometry and single cell RNA sequencing
Project description:BackgroundIn our previous study that characterized different human CD4+ lymphocyte preparations, it was found that both commercially available cryopreserved peripheral blood mononuclear cells (PBMC) and a commercially available lyophilized PBMC (Cyto-Trol™) preparation fulfilled a set of criteria for serving as biological calibrators for quantitative flow cytometry. However, the biomarker CD4 protein expression level measured for T helper cells from Cyto-Trol was about 16% lower than those for cryopreserved PBMC and fresh whole blood using flow cytometry and mass cytometry. A primary reason was hypothesized to be due to steric interference in anti- CD4 antibody binding to the smaller sized lyophilized control cells.MethodTargeted multiple reaction monitoring (MRM) mass spectrometry (MS) is used to quantify the copy number of CD4 receptor protein per CD4+ lymphocyte. Scanning electron microscopy (SEM) is utilized to assist searching the underlying reasons for the observed difference in CD4 receptor copy number per cell determined by MRM MS and CD4 expression measured previously by flow cytometry.ResultsThe copy number of CD4 receptor proteins on the surface of the CD4+ lymphocyte in cryopreserved PBMCs and in lyophilized control cells is determined to be (1.45 ± 0.09) × 10(5) and (0.85 ± 0.11) × 10(5), respectively, averaged over four signature peptides using MRM MS. In comparison with cryopreserved PBMCs, there are more variations in the CD4 copy number in lyophilized control cells determined based on each signature peptide. SEM images of CD4+ lymphocytes from lyophilized control cells are very different when compared to the CD4+ T cells from whole blood and cryopreserved PBMC.ConclusionBecause of the lyophilization process applied to Cyto-Trol control cells, a lower CD4 density value, defined as the copy number of CD4 receptors per CD4+ lymphocyte, averaged over three different production lots is most likely explained by the loss of the CD4 receptors on damaged and/or broken microvilli where CD4 receptors reside. Steric hindrance of antibody binding and the association of CD4 receptors with other biomolecules likely contribute significantly to the nearly 50% lower CD4 receptor density value for cryopreserved PBMC determined from flow cytometry compared to the value obtained from MRM MS.
Project description:Adaptive immune responses are complex dynamic processes whereby B and T cells undergo division and differentiation triggered by pathogenic stimuli. Deregulation of the response can lead to severe consequences for the host organism ranging from immune deficiencies to autoimmunity. Tracking cell division and differentiation by flow cytometry using fluorescent probes is a major method for measuring progression of lymphocyte responses, both in vitro and in vivo. In turn, mathematical modeling of cell numbers derived from such measurements has led to significant biological discoveries, and plays an increasingly important role in lymphocyte research. Fitting an appropriate parameterized model to such data is the goal of these studies but significant challenges are presented by the variability in measurements. This variation results from the sum of experimental noise and intrinsic probabilistic differences in cells and is difficult to characterize analytically. Current model fitting methods adopt different simplifying assumptions to describe the distribution of such measurements and these assumptions have not been tested directly. To help inform the choice and application of appropriate methods of model fitting to such data we studied the errors associated with flow cytometry measurements from a wide variety of experiments. We found that the mean and variance of the noise were related by a power law with an exponent between 1.3 and 1.8 for different datasets. This violated the assumptions inherent to commonly used least squares, linear variance scaling and log-transformation based methods. As a result of these findings we propose a new measurement model that we justify both theoretically, from the maximum entropy standpoint, and empirically using collected data. Our evaluation suggests that the new model can be reliably used for model fitting across a variety of conditions. Our work provides a foundation for modeling measurements in flow cytometry experiments thus facilitating progress in quantitative studies of lymphocyte responses.
Project description:BackgroundMesenchymal stem/stromal cells (MSC) have immunomodulatory properties, studied in a wide range of diseases. Validated quality controls must confirm this activity in the context of clinical trials. This study presents a method's validation, assessing MSC's ability to inhibit lymphocyte proliferation, according to the ICH Q2 standard.MethodsMSC were co-cultured with CellTrace™ Violet-labeled Peripheral blood mononuclear cells (PBMC) coming from a bank of ten donors, at seven different ratios for 7 days. Cell trace violet PBMC bank was validated in parallel. Flow cytometry analysis was used to obtain the division percentage of T cells. The percentage of inhibition of lymphocyte proliferation by MSC, for each ratio X, was calculated using the formula: Ratio × percentage of inhibition = (control percentage of division-ratio × percentage of division)/control percentage of division. The inhibition percentage of lymphocyte proliferation function of co-culture ratios was represented in a line graph. The corresponding area under the curve was calculated, representing MSC's ability to inhibit lymphocyte proliferation.ResultsTwo cell trace violet PBMC banks were compared for bank validation. When compared using four different MSC samples coming each from a different donor, their area under the curve did not show any statistical differences and were correlated. Moreover, the stability of one cell trace violet PBMC bank was confirmed up to 509 days of storage. Analytical parameters were investigated for method validation. Analysis of repeatability and reproducibility respectively showed a standard deviation of 6.1% and 4.6%. The assay was robust regarding PBMC, as no statistical differences were found between inhibitory activities when testing three adjacent concentrations of PBMC. Still, attention is needed on MSC quantity as it can influence results. Linearity was evaluated: the percentage of inhibition of lymphocyte proliferation function of co-culture ratios was linear on the exploited range. Finally, the assay measurement range allowed to differentiate MSC presenting different inhibition activities.ConclusionThis quantification method displayed low analytical variability and no inter-bank variability of PBMC. However, MSC quantification should be checked before co-culture to reduce variability. Therefore, it could be used for the qualification of MSC batches' immunomodulatory activity.
Project description:The spatial heterogeneity of immune microenvironment in hepatocellular carcinoma (HCC) remains elusive. Here, a single-cell study involving 17 432 600 immune cells of 39 matched HCC (T), nontumor (N), and leading-edge (L) specimens by mass cytometry is conducted. The tumor-associated CD4/CD8 double-positive T (DPT) cells are found enriched in L regions with synergetic expression of PD-1/HLA-DR/ICOS/CD45RO and exhibit a higher level of IFN-γ, TNF-α, and PD-1 upon stimulation. The enrichment of DPT and PD-1+DPT in L regions indicates favorable prognosis. These tumor-associated DPT cells with similar phenotype are also verified in other tumors and HCC animal models. Single-cell RNA-seq further characterizes the molecular features of DPT cells and uncovers 11 clusters with different cytotoxicity, exhaustion, and activation scores. TCR-based trajectory analysis reveals that tumor-associated DPT clusters share separated ancestries with local CD4+ or CD8+SPT cells rather than CD3+PBMC cells. TCR clones with frequency above 10 are mainly found coexisting in DPT and CD8+SPT cells. Specifically, PD-1highDPT cluster (TDPT_10) shares the same ancestry with exhausted CD8+SPT cluster (TCD8T_2) and shows higher expression similarity and closer pathological location to PD-1+CD8+ than PD-1+CD4+T cells. Together, this study systematically characterizes the unique distribution of PD-1+DPTs in HCC and puts forward new insights for the function and origin of tumor-associated DPT cells.
Project description:T cells secrete bioactive exosomes (EXO), but the potential immunoregulatory effect of T-cell EXO is largely unknown. In this study, we generated activated ovalbumin (OVA)-specific CD4(+) T cells in vitro via coculture of OVA-pulsed dendritic cells (DC(OVA)) with naive CD4(+) T cells derived from OVA-specific T-cell receptor (TCR) transgenic OTII mice. CD4(+) T-cell EXO were then purified from the CD4(+) T-cell culture supernatants by differential ultracentrifugation. CD4(+) T-cell EXO exhibited the 'saucer' shape that is characteristic of EXO with a diameter between 50 and 100 nm, as assessed by electron microscopy, and contained the EXO-associated proteins LAMP-1, TCR and lymphocyte function associated antigen-1 (LFA-1), as determined by western blot. Flow cytometric analysis showed that CD4(+) T-cell EXO expressed CD4(+) T-cell markers (CD4, TCR, LFA-1, CD25 and Fas ligand), but to a lesser extent than CD4(+) T cells. We demonstrated that DC(OVA) took up CD4(+) T-cell EXO via peptide/major histocompatibility complex (pMHC) II/TCR and CD54/LFA-1 interactions. OVA-specific CD4(+) T-cell EXO from OTII mice, but not ConA-stimulated polyclonal CD4(+) T-cell EXO from wild-type C57BL/6 mice inhibited DC(OVA)-stimulated in vitro CD4(+) T-cell proliferation and in vivo CD8(+) cytotoxic T lymphocyte (CTL) responses and antitumor immunity against OVA-expressing B16 melanoma BL6-10(OVA) cells. In addition, EXO derived from a T-cell hybridoma cell line, MF72.2D9, expressing an OVA-specific CD4(+) TCR, had a similar inhibitory effect as OTII CD4(+) T-cell EXO on CTL-mediated antitumor immunity. Taken together, our data indicate that antigen-specific T-cell EXO may serve as a new type of immunosuppressive reagent for use in transplant rejection and treatment of autoimmune diseases.
Project description:BackgroundThe combination of CTLA-4 and PD-L1 inhibitors has a manageable adverse effect profile, although rare immune-related adverse events (irAE) can occur.Case presentationWe describe an autoimmune polymyositis following a partial response to combination tremelimumab and durvalumab for the treatment of recurrent lung adenocarcinoma. Radiography revealed significant reduction in all metastases; however, the patient developed progressive neuromuscular hypoventilation due to lymphocytic destruction of the diaphragmatic musculature. Serologic testing revealed a low level of de novo circulating antibodies against striated muscle fiber. Immunohistochemistry revealed type II muscle fiber atrophy with a mixed CD8+ and CD4+ lymphocyte infiltrate, indicative of inflammatory myopathy.ConclusionsThis case supports the hypothesis that muscle tissue is a target for lymphocytic infiltration in immune checkpoint inhibitor-associated polymyositis. Further insights into the autoimmune mechanism of PM will hopefully contribute to the prevention and treatment of this phenomenon.
Project description:Epitope escape from HIV-1-targeted CD8+ cytotoxic T lymphocyte (CTL) responses occurs rapidly after acute infection and contributes to the eventual failure of effective immune control of HIV-1 infection. Because the early CTL response is key in determining HIV-1 disease outcome, studying the process of epitope escape is crucial for understanding what leads to failure of immune control in acute HIV-1 infection and will provide important implications for HIV-1 vaccine design. HIV-1-specific CD8+ T lymphocyte responses against viral epitopes were mapped in six acutely infected individuals, and the magnitudes of these responses were measured longitudinally during acute infection. The evolution of autologous circulating viral epitopes was determined in four of these subjects. In-depth testing of CD8+ T lymphocyte responses against index and all autologous-detected variant epitopes was performed in one subject. Among the four individuals examined, 10 of a total of 35 CD8+ T cell responses within Gag, Pol, and Nef showed evidence of epitope escape. CTL responses with viral epitope variant evolution were shown in one subject, and this evolution occurred with and without measurable CTL responses against epitope variants. These results demonstrate a dynamic period of viral epitope evolution in early HIV-1 infection due to CD8+ CTL response pressure.
Project description:IntroductionThe leukocyte adhesion cascade is important for the maintenance of homeostasis and the ability of immune cells to access sites of infection and inflammation. Despite much work identifying the molecular components of the cascade, and numerous simulations to predict the relationship between molecule density, identity, and adhesion, these relationships have not been measured experimentally.MethodsUsing surfaces functionalized with recombinant ICAM-1 and/or E-selectin along with immobilized SDF-1α, we used a flow chamber to measure rates of tethering, rolling and arrest of primary naïve human CD4+ T lymphocytes on different surface densities of ligand.ResultsCells required a minimum level of ligand density to progress beyond tethering. E-selectin and ICAM-1 were found to have a synergistic relationship in promoting cell arrest. Surfaces with both ligands had the highest levels of arrest, while surfaces containing only E-selectin hindered the cell's ability to progress beyond rolling. In contrast, surfaces of ICAM-1 allowed only tethering or arrest. Cells maintained constant rolling velocity and time to stop over large variations in surface density and composition. In addition, surface densities of only O(101) sites/μm2 allowed for rolling while surface densities of O(102) sites/μm2 promoted arrest, approximately equal to previously determined simulated values.ConclusionsWe have systematically and experimentally mapped out the state diagram of T-cell adhesion under flow, directly demonstrating the quantitative requirements for each dynamic state of adhesion, and showing how multiple adhesion molecules can act in synergy to secure arrest.