CVID patients with autoimmunity have elevated T cell expression of granzyme B and HLA-DR and reduced levels of Treg cells

2012 ◽  
Vol 66 (2) ◽  
pp. 146-150 ◽  
Author(s):  
Clive R D Carter ◽  
Ganesha Aravind ◽  
Natuley L Smalle ◽  
June Y Cole ◽  
Sinisa Savic ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Granzyme B ◽  
Treg Cells ◽  
T Cell Subsets ◽  
Activated T Cells ◽  
Activation Markers ◽  
Hla Dr

AimsCommon variable immunodeficiency (CVID) is a primary antibody immunodeficiency with approximately 20% of patients reporting additional autoimmune symptoms. The primary aim of this study was to compare the levels of activated and regulatory T cells (Treg cells) in CVID patients in an attempt to clarify their possible interactions leading to the generation of autoimmunity.MethodsImmunophenotyping of T cells was performed by flow cytometry using a whole blood approach. Surface expression of human leukocyte antigen HLA class II DR and intracellular levels of granzyme B in T cell subsets were assessed; Treg levels were measured using CD4 CD25, FOXp3 and CTLA-4.ResultsCVID patients had higher levels of granzyme B and HLA-DR on CD8+ T cells compared with control values (mean of 59% vs 30% and 45% vs 21%, respectively). Patients also had reduced levels of Treg cells compared with control values (con mean=3.24% vs pat=2.54%). Patients with autoimmunity (5/23) had a similar level of T cell activation markers to the rest of the patients but with lower Treg cells (mean of 1.1%) and reduced CD25 and CTLA-4 expression. Patients with autoimmunity had a higher ratio of activated to Treg cells compared with patients with no autoimmune symptoms.ConclusionsThese results highlight that reduced levels of Treg cells were associated with elevated levels of activated T cells, suggesting that reduced Treg cells in these patients may have functional consequences in allowing exaggerated T cell responses.

scholarly journals HIV and Tuberculosis co-infection impacts T-cell activation markers but not the numbers subset of regulatory T-cells in HIV-1 infected patients

2013 ◽  
Vol 2 (1) ◽  
Author(s):  
Moustapha Mbow ◽  
Ndèye S.S. Santos ◽  
Makhtar Camara ◽  
Awa Ba ◽  
Aliou Niang ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Regulatory T Cells ◽  
Hiv Infection ◽  
T Cell Activation ◽  
Cell Activation ◽  
Treg Cells ◽  
Activation Markers ◽  
Hla Dr ◽  
Hiv 1

Background: Tuberculosis (TB) has been shown to accelerate the clinical course of HIV infection, but the mechanisms by which this occurs are not well understood. Regulatory T-cells (Tregs)are known to dampen hyperactivation of the immune cells, but it remains unclear whether hyperactivation of T-cells in HIV infection is associated with a decrease of Tregs and what the effect Mycobacterium tuberculosis (MTB) co-infection has on T-cell activation and Tregs.Objectives: In this study, we aim to evaluate whether active TB is associated with the increased expression of T-cell activation markers and reduced number of Treg cells in HIV-1-infected patients.Methods: This study was conducted on 69 subjects consisting of 20 HIV-infected patients,20 HIV and MTB co-infected patients, 19 MTB-infected patients and 10 uninfected control subjects negative for both MTB and HIV. The frequencies of T-cell activation markers (CD38 and HLA-DR) and Treg cells (CD4+CD25+CD127-) were measured by flow cytometry.Results: Significantly higher expression of CD38 and HLA-DR on CD4+ and CD8+ T-cells was found in MTB and HIV co-infected patients compared with HIV-infected patients. However,no significant difference in the percentage of Treg cells was reported between HIV patients with TB and those without. The study also showed a negative correlation between regulatoryT-cells frequency and CD4+ T-cell counts.Conclusion: These results suggest that TB enhances the expression of peripheral T-cell activation markers during HIV infection, whilst having no impact on the percentages of Tregcells.

scholarly journals Rapid Flow Cytometry Method for Quantitation of LFA-1-Adhesive T Cells

2006 ◽  
Vol 13 (3) ◽  
pp. 403-408 ◽  
Author(s):  
Brian Crucian ◽  
Mayra Nelman-Gonzalez ◽  
Clarence Sams
Keyword(s):  
Flow Cytometry ◽  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
T Cell Subsets ◽  
Activated T Cells ◽  
Peripheral Blood Mononuclear ◽  
Simple Method ◽  
Rapid Flow

ABSTRACT Adhesion molecules are important for leukocyte endothelial attachment and migration to sites of inflammation. The LFA-1 (CD11a and CD18) integrin molecule is constitutively expressed on the T-cell surface. Following T-cell activation, a rapid conformational change of LFA-1 to an “adhesive” state occurs, allowing LFA-1 binding to intracellular cell adhesion molecule type 1 (ICAM-1)-expressing targets, such as antigen-presenting cells. For this study, a rapid flow cytometry method for the quantitation of LFA-1-adhesive T cells following activation was developed. Purified ICAM-1 was bound to 4.5-μm-diameter beads. Following peripheral blood mononuclear cell activation culture (phorbol myristate acetate and ionomycin), the cells were incubated with the ICAM-1 beads, which allowed attachment to occur. The T cell-bead complexes were then resolved from unbound T cells by flow cytometry. Multicolor analysis allowed a complete phenotypic analysis of the adhesive T-cell subsets. Experimental controls indicated that the T cell-bead attachment was LFA-1 and ICAM-1 specific. Very little binding between unactivated T cells and ICAM beads or between activated T cells and plain beads was observed. The kinetics of the response was extremely rapid, with nearly maximal numbers of adhesive T cells observed following 5 min of activation. Scanning electron microscopy analysis was used to characterize legitimate bead-cell binding. By using multicolor cytometry, the responding adhesive T-cell population was usually identified as a distinct subset of T cells with the following phenotype: CD3+ CD4+ or CD8+ CD19− CD16− CD45RO+ CD62L+ CD27+ CD57−. A rapid and simple method for the scoring of LFA-1-adhesive T cells was developed and may have significant utility for immune function studies.

scholarly journals Increased state of activation of CD4 positive T cells and elevated interferon γ production in pouchitis

Gut ◽  
1998 ◽  
Vol 43 (4) ◽  
pp. 499-505 ◽  
Author(s):  
A Stallmach ◽  
F Schäfer ◽  
S Hoffmann ◽  
S Weber ◽  
I Müller-Molaian ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Mononuclear Cells ◽  
Interferon Γ ◽  
Ileoanal Pouch ◽  
T Cell Subsets ◽  
Activation Markers ◽  
Ifn Γ

Background—Immunoregulatory abnormalities of T cells might be of importance in the pathogenesis of pouchitis after ileoanal pouch anastomosis (IAP).Aims—To characterise T cell subsets, their state of activation, and production of cytokines in inflamed and non-inflamed pouches in patients with ulcerative colitis (UC) and familial adenomatous polyposis (FAP). The influence of T cell activation on mucosal transformation was also studied.Patients—Mucosal biopsy specimens were taken from 42 patients with IAP (33 with UC and nine with FAP).Methods—Mononuclear cells were isolated by standard techniques and characterised by three colour flow cytometry. Interferon γ (IFN-γ) production was studied using the ELISPOT technique.Results—In patients with UC with pouchitis there was a significant increase in the CD4:CD8 ratio, expression of activation markers on CD3+ cells, and number of IFNγ producing mononuclear cells compared with patients with UC without pouchitis (CD4:CD8 ratio 1.3 (range 0.7–2.7) versus 0.6 (0.1–1.0), p=0.012). In addition, a positive correlation between increased crypt depth and the number of CD4+ cells (r=0.57) was shown.Conclusion—The observed increase in activated mucosal CD4+ T cells and IFN-γ production might lead to mucosal destruction and crypt hyperplasia as seen in pouchitis.

Shedded neuronal ICAM-5 suppresses T-cell activation

Blood ◽  
2008 ◽  
Vol 111 (7) ◽  
pp. 3615-3625 ◽  
Author(s):  
Li Tian ◽  
Jani Lappalainen ◽  
Matti Autero ◽  
Satu Hänninen ◽  
Heikki Rauvala ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Cell Receptor ◽  
Soluble Form ◽  
Mammalian Brain ◽  
Activated T Cells ◽  
Activation Markers ◽  
Costimulatory Signals

Abstract Intercellular adhesion molecules (ICAMs) bind to leukocyte β2 integrins, which, among other functions, provide costimulatory signals for T-cell activation. ICAM-5 (telencephalin) is expressed in the somadendritic region of neurons of the mammalian brain. The receptor for ICAM-5 is the integrin LFA-1, a major leukocyte integ-rin expressed in lymphocytes and microglia. In conditions of brain ischemia, epilepsy, and encephalitis, the soluble form of ICAM-5 (sICAM-5) has been detected in physiologic fluids. Here, we report that sICAM-5 attenuates the T-cell receptor-mediated activation of T cells as demonstrated by the decreased expression of the activation markers CD69, CD40L, and CD25 (IL-2R). This effect is most clearly seen in CD45ROLow (naive), and not in CD45ROHigh (memory) T cells, and is most effective early in priming, but not in the presence of strong costimulatory signals. Furthermore, sICAM-5 promotes the mRNA expression of the cytokines TGF-β1 and IFN-γ, but not TNF. The formation of sICAM-5 is promoted by activated T cells through the cleavage of ICAM-5 from neurons. This suggests that ICAM-5 is involved in immune privilege of the brain and acts as an anti-inflammatory agent.

scholarly journals CD4+ T-Cell Subsets That Mediate Immunological Memory to Mycobacterium tuberculosis Infection in Mice

2000 ◽  
Vol 68 (2) ◽  
pp. 621-629 ◽  
Author(s):  
Peter Andersen ◽  
Birgitte Smedegaard
Keyword(s):  
T Cells ◽  
Mycobacterium Tuberculosis ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Immunological Memory ◽  
T Cell Subsets ◽  
Small Subset ◽  
Memory Cells ◽  
Activation Markers

ABSTRACT We have studied CD4+ T cells that mediate immunological memory to an intravenous infection with Mycobacterium tuberculosis. The studies were conducted with a mouse model of memory immunity in which mice are rendered immune by a primary infection followed by antibiotic treatment and rest. Shortly after reinfection, tuberculosis-specific memory cells were recruited from the recirculating pool, leading to rapidly increasing precursor frequencies in the liver and a simultaneous decrease in the blood. A small subset of the infiltrating T cells was rapidly activated (<20 h) and expressed high levels of intracellular gamma interferon and the T-cell activation markers CD69 and CD25. These memory effector T cells expressed intermediate levels of CD45RB and were heterogeneous with regard to the L-selectin and CD44 markers. By adoptive transfer into nude mice, the highest level of resistance to a challenge with M. tuberculosis was mediated by CD45RBhigh,l-selectinhigh, CD44low cells. Taken together, these two lines of evidence support an important role for memory cells which have reverted to a naive phenotype in the long-term protection against M. tuberculosis.

scholarly journals Upregulation of Phosphodiesterase 2A Augments T Cell Activation by Changing cGMP/cAMP Cross-Talk

2021 ◽  
Vol 12 ◽  
Author(s):  
Roberta Kurelic ◽  
Paula F. Krieg ◽  
Jana K. Sonner ◽  
Gloria Bhaiyan ◽  
Gustavo C. Ramos ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cross Talk ◽  
Cell Activation ◽  
Inflammatory Responses ◽  
T Cell Subsets ◽  
Activation Markers ◽  
Tcr Activation ◽  
Camp Levels

3′,5′-cyclic adenosine monophosphate (cAMP) is well-known for its diverse immunomodulatory properties, primarily inhibitory effects during T cell activation, proliferation, and production of pro-inflammatory cytokines. A decrease in cAMP levels, due to the hydrolyzing activity of phosphodiesterases (PDE), is favoring inflammatory responses. This can be prevented by selective PDE inhibitors, which makes PDEs important therapeutic targets for autoimmune disorders. In this study, we investigated the specific roles of PDE2A and PDE3B in the regulation of intracellular cAMP levels in different mouse T cell subsets. Unexpectedly, T cell receptor (TCR) activation led to a selective upregulation of PDE2A at the protein level in conventional T cells (Tcon), whereas no changes were detected in regulatory T cells (Treg). In contrast, protein expression of PDE3B was significantly higher in both non-activated and activated Tcon subsets as compared to Treg, with no changes upon TCR engagement. Live-cell imaging of T cells expressing a highly sensitive Förster resonance energy transfer (FRET)-based biosensor, Epac1-camps, has enabled cAMP measurements in real time and revealed stronger responses to the PDE2A inhibitors in activated vs non-activated Tcon. Importantly, stimulation of intracellular cGMP levels with natriuretic peptides led to an increase of cAMP in non-activated and a decrease of cAMP in activated Tcon, suggesting that TCR activation changes the PDE3B-dependent positive to PDE2A-dependent negative cGMP/cAMP cross-talk. Functionally, this switch induced higher expression of early activation markers CD25 and CD69. This constitutes a potentially interesting feed-forward mechanism during autoimmune and inflammatory responses that may be exploited therapeutically.

Demonstration of a Direct Immunomodulatory Role for Vitamin D in Human T Cells Using Flow Cytometry

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2577-2577
Author(s):  
Richard W. Joseph ◽  
Tae Kon Kim ◽  
Lisa St. John ◽  
Jahan Khalili ◽  
Uday R Popat ◽  
...  
Keyword(s):  
Vitamin D ◽  
Flow Cytometry ◽  
Cell Proliferation ◽  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
T Cell Proliferation ◽  
Activated T Cells ◽  
Activation Markers

Abstract Clinical and epidemiological studies have demonstrated an increasingly stronger link between Vitamin D deficiency and a broad array of illnesses characterized by inflammation, including autoimmune diseases, coronary artery disease, and cancers. Vitamin D is a steroid hormone that exerts the majority of its biologic effects via the binding of the intracellular Vitamin D receptor (VDR). While upregulation of VDR has been demonstrated in activated bulk T cells using traditional approaches (e.g., western blotting), such assays cannot precisely define VDR distribution and kinetics. To overcome these limitations, we developed what we believe to be the first flow cytometric assay to quantify VDR expression at a single-cell level. We used a primary antibody against VDR (mouse monoclonal IgG2a to human VDR) in permeabilized T cells followed by a labeled secondary antibody. We detected a positive cell population using flow cytometry that was sharply increased following activation, consistent with upregulation of VDR confirmed by immunoblotting of sorted cells. We then applied this validated assay to define the kinetics of VDR upregulation in activated T cells. We stimulated PBMC with PMA:Ionomycin (P:I) for varying intervals and assessed intracellular VDR using flow cytometry. VDR is significantly upregulated by 15 min after stimulation, reaches a plateau after 6 hr, and may remain elevated for up to 7 d. We compared VDR to classical early and late T cell activation markers (CD69 and CD25, respectively), and we found that VDR was upregulated as consistently as (but even earlier than) CD69, and that VDR and CD25 were both consistently upregulated at later intervals (p&lt;0.0001). To examine the association between VDR expression and proliferation, we stimulated CFSE-labeled T cells with OKT3 (2mg/ml) for 5 d and found that proliferating T cells expressed a significantly higher level of VDR than resting T cells, which maintained baseline VDR expression (p&lt;0.0001). To assess the association between T cell cytokine production and VDR expression, we stimulated T cells with (P:I) for 6 hr in the presence of brefeldin A, and we confirmed that all cytokine-producing cells (TNFα, IL-2, IFNγ) were contained within the VDR-high population. We then assessed whether physiologic concentrations of Vitamin D could inhibit T cell proliferation in vitro. We stimulated CFSE-labeled PBMC with either OKT3 or irradiated allogeneic dendritic cells (DC) in the presence or absence of physiologic concentrations of calcitriol (50 nm) for 5 to 7 d. The presence of calcitriol during OKT3 stimulation resulted in significantly reduced cell division (p=0.004, n=5). Using a previously validated phenotype to demarcate activated alloreactive CD4+ T cells (CD4hiCD38+), we demonstrated that physiologic calcitriol supplementation decreased alloreactive activation following 7 d stimulation with allogeneic DC (p=0.0003, n=10). In conclusion, VDR is a consistent and specific early and late marker of T cell activation, suggesting a direct role for the Vitamin D axis in immunoregulation. Furthermore, physiological concentrations of Vitamin D can inhibit T cell proliferation induced by polyclonal stimuli, including allogeneic DC. These data provide confirmation for a direct immunoregulatory role for Vitamin D and suggest that further mechanistic and clinical studies may yield novel therapeutic strategies for inflammatory conditions, including graft-versus-host disease.

Peripheral blood T cell activation after radioiodine treatment for Graves' disease

1990 ◽  
Vol 122 (2) ◽  
pp. 233-240 ◽  
Author(s):  
Wei-Ping Teng ◽  
Roger Stark ◽  
AlistairJ. Munro ◽  
Stuart McHardy Young ◽  
Leszeck K. Borysiewicz ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Antithyroid Drug ◽  
Significant Rise ◽  
T Cell Subsets ◽  
Graves Disease ◽  
Variable Response ◽  
Activated T Cells

Abstract Radioiodine therapy for Graves' thyrotoxicosis produces a rise in thyroid autoantibodies in the first three months after treatment, but little is known of its effects on T cells. We have therefore followed the changes in T cell subsets in sequential samples from 23 patients with Graves' disease treated with radioiodine, using dualcolour flow cytometry. In the first month after treatment there was a significant rise in activated T cells, identified by the markers HLA-DR (la) and CDw26/Tal (p<0.025 in both cases). CD45RO-positive T cells, which are the primed population containing memory cells, also increased (p<0.025), but there was no change in CD45R-positive, resting T cells or in the CD4 to CD8 (helper to cytotoxic/suppressor) ration. Vicia villosa-binding T cells, containing the contrasuppressor population, showed a more variable response, but the trend was to an overall increase from pre-treatment values (p<0.025). The changes did not appear to be related to antithyroid drug treatment, since they were seen irrespective of whether patients continued such therapy. These results suggest that T cell activation and enhanced contrasuppressor activity may in part be responsible for the rise in autoantibodies after radioiodine. The T cell changes could also contribute to the worsening of ophthalmopathy seen in some radioiodine-treated patients.

Induction of Mouse Naive T Cells Transition into CD4+ CD2+ FoxP3+ Regulatory T Cells in a Modified Culture Medium As a Potential Armament in Graft-Versus-Host Disease

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5426-5426
Author(s):  
Tzeon-Jye Chiou ◽  
Tan-Hwa Chu ◽  
Sin-Tak Chu ◽  
Woan-Fang Tzeng
Keyword(s):  
T Cells ◽  
T Cell ◽  
Regulatory T Cells ◽  
T Cell Activation ◽  
Cd4 T Cells ◽  
Cell Activation ◽  
Foxp3 Expression ◽  
Treg Cells ◽  
Activated T Cells ◽  
Allogeneic Hsct

Abstract Allogeneic hematopoietic stem cell transplantation (HSCT) has been used to treat some of hematological malignancies and inherited or acquired non-malignant disorders. Unfortunately, graft-versus-host disease (GVHD) occurred approximately 15% in transplant recipients and impacts on the outcome of allogeneic HSCT. At present, no effective modality could completely prevent the GVHD from allogeneic HSCT patients. CD4+ CD25+ FoxP3+ regulatory T cells (Tregs) have been shown to be important in maintaining immune homeostasis and preventing autoimmunity. However, 5% to 10% Tregs could be measured in human CD4+ T cells and few Tregs would convert to conventional activated T cells because of losing FoxP3 expression orn Tregs in suppression of T cell activation. It had been reported to correlate with the occurrence and severity of GVHD in some study. In order to study the potential use of CD4+ CD25+ FoxP3+ Tregs for the prevention of GVHD, we attempt to evaluate the better efficient method to increase the number of induced Treg cells (i Tregs) in donor and stabilize the FoxP3 ini Treg cells. Using mouse as a model, the splenocytes were prepared from mouse spleen. Before having biological function,i Treg cells need to stabilize the FoxP3 protein expression. Using retinoic acid (RA, 0.1-5ng/ml) as a stabilizer of the FoxP3 protein expression can keep thei Treg cells in stable. The endogenous regulatory T cells (n Treg) can inhibit T cell activation, thereby affecting T cells intoi Treg efficiency. We should remove the n Treg cells from the CD4+ T cells. Therefore, CD4+ T cells were isolated by negative selection, and then using the n Treg removing kit, we harvested the CD4+ CD62L+ naïve T cells fori Treg cell induction. For this purpose, naïve CD4+ cells were harvested, and then activated with anti-CD3/CD28 Dynabeads in the presence of IL-2, TGF-β1 and retinoic acid (RA) containing RPMI1640 medium. During the Tregs induction, the activated T cells were performed under low nutrient supplement (5% FBS) for three days then refreshed the cells into the full nutrient supplement (10% FBS) for another four days. The harvested cells were analyzed by flow cytometry method with fluorescence-conjugated CD-antibodies, including CD4, CD25, CD127, CD62L and FoxP3. Currently, the removal of n Treg cells could improve the efficiency of i Treg cell formation from 15% to 70-80% under this modified culture method (Fig.1). Further improvement of human peripheral blood regulatory T cell generation efficiency is our ongoing target. Our study showed that the combination of IL-2, TGF-β1 and RA in 3-day-nutrient-deprived medium could convert naïve CD4+ CD62L+ T cells to CD4+ CD25+ FoxP3+i Treg cells and stabilize FoxP3 expression in thei Treg cells efficiently. Further, we will develop thei Treg suppression assay to clarify the biological function ofi Tregs in vitro. GVHD mouse model will be established by using allogeneic HSCT to verify the function of i Tregs in vivo, too. Disclosures No relevant conflicts of interest to declare.

scholarly journals T Cell Activation By OKT3 Is a Function of the Percent Monocytes in PBMC of Healthy Donors and MDS Patients

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4870-4870
Author(s):  
Alison Tarke ◽  
Valentina Ferrari ◽  
Hannah Fields ◽  
Luca Ferrari ◽  
Franco Ferrari ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Cell Transplant ◽  
Activation Markers ◽  
Hematopoietic Stem ◽  
Hla Dr ◽  
Healthy Donors

Background: Myelodysplastic Syndromes (MDS) are a heterogeneous hematologic malignancy characterized by bone marrow failure and cytopenias. The median survival rate for patients with higher-risk MDS who fail standard-of-care chemotherapy with hypomethylating agents (HMAs) is less than 6 months, and the only curative treatment for these patients is hematopoietic stem cell transplant (HSCT). Over the past 10 years, immunotherapy as a cancer treatment has achieved variable levels of success in different tumor types. There are currently 22 active clinical trials of immunotherapies for MDS (www.clinicaltrials.gov; 7/30/19), including our phase I clinical trial with a personalized adoptive cellular therapy targeting MDS patient neoantigens (NCT 03258359). Because MDS patients are frequently monocytopenic and the existing literature is inconsistent regarding the ability of MDS patients' monocytes to support T cell activation, we compared the activation of MDS T cells with those of healthy donors in the presence of autologous monocytes. Methods: Peripheral blood mononuclear cells (PBMC) from 5 healthy donors and 7 higher-risk MDS patients were cryopreserved after Ficoll separation. These PBMC were thawed and aliquoted into 6 replicate wells of 200,000 cells in 96-well u-bottom plates in R-10 culture medium. Half of the wells were treated with 25 ng/mL OKT3 and 200 U/mL IL-2. After 48 hours at 37˚C with 5% CO2, the wells were collected for analysis by flow cytometry. Beads were used to detect T cell activation induced secretion of IFNg, TNFa, IL-4, IL-10, and IL-17 in the supernatant and fluorescent antibodies were used to phenotype viable cells for CD3, CD4, CD8, and the T cell activation markers, CD69, CD25, CTLA-4, PD-1, and HLA-DR. Results: We measured a higher release of IFNg and TNFa in donor PBMC compared to MDS patients after OKT3/IL-2 activation, p < 0.01 and 0.04, respectively by 2-way ANOVA. The expression of CD69, CD25, HLA-DR, and CTLA4 increased variably on activated T cells from donors or MDS patients, but expression of CD4+CD25+ was more frequent on donor T cells after activation (p = 0.03). Activation also resulted in a higher frequency of PD-1 expression on donor CD4+ and CD8+ T cells than on MDS T cells (p < 0.01 and < 0.01, respectively). Interestingly, on both MDS and normal T cells the percentage of CD8+PD1+ activated cells correlated strongly with the percent of CD14+ monocytes present in the PBMC (R2 = 0.92 and 0.60 respectively; Fig 1a and 1b). We designed further experiments to test whether this was a patient intrinsic phenomenon, or if the absolute number of CD14+ monocytes in the PBMC was associated with different levels of PD1 expression upon T cell activation. First, we separated CD14+ cells from the PBMC of a patient with MDS using magnetic beads. Then CD14+ cells were added back to the CD14-depleted PBMC at a final percent of 0.5, 5, 10, 20, 35, 70, or 100% of the original amount. Unmodified PBMC was included as a control and all cells were stimulated with OKT3 and IL-2 or left in R-10 medium without stimulus. After 24, 48, and 70 hours, samples were collected to analyze by flow cytometry for CD3, CD4, CD8, CD14, and PD1 expression. The results show that an increasing percent of monocytes corresponded to the increased expression of PD1 on CD8+ and CD4+ T cells. Conclusion: Our results show that there are variable reductions in markers of T cell activation and cytokine secretion in MDS patients compared to healthy donors. We also observed that the fold increase in activation induced PD-1 expression was well correlated with the percent of CD14+ monocytes in the PBMC of both MDS patients and healthy donors. Direct experimentation revealed that this correlation is a cause-effect relationship. We are continuing to investigate the role of monocytes in T cell activation in MDS patients. Disclosures Bejar: Celgene: Consultancy; Takeda Pharmaceuticals: Research Funding; AbbVie/Genentech: Consultancy, Honoraria; Astex/Otsuka: Consultancy; Modus Outcomes: Consultancy; Daiichi-Sankyo: Consultancy. Lane:PersImmune, Inc.: Employment.

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