747 Evaluation of immune microenvironment of primary lung cancer and synchronous liver metastasis with multispectral imaging system

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A795-A795
Author(s):  
Hyeonbin Cho ◽  
Jae-Hwan Kim ◽  
Ji-Hyun Kim
Keyword(s):  
T Cells ◽  
Liver Metastasis ◽  
Multispectral Imaging ◽  
Immune Cell ◽  
Imaging System ◽  
Cytotoxic T Cells ◽  
Primary Lung Cancer ◽  
Helper T Cells ◽  
Synchronous Liver Metastasis ◽  
Immune Microenvironment

BackgroundCancer immunotherapy (CIT) has substantially improved the survival of cancer patients. However, according to recent studies, liver metastasis was reported to predict worse outcomes for CIT. The main objective of the study is to evaluate the differences in the immune microenvironment (IME) between the primary lung cancer (PL) and synchronous liver metastasis (LM) using a multispectral imaging system.MethodsSix immune markers (CD4, CD8, CTLA-4, granzyme B (GZB), Foxp3 and PD-L1) were analyzed using a multiplex IHC system and inForm program (Akoya) on paired lung-liver samples of 10 patients. Cells were categorized into tumor nest and stroma, and cell counts per unit area were measured for comparison.ResultsThe number of tumor-infiltrating cytotoxic T cells (TIL) in PL (262.5 cells/mm2) was higher than that of LM (113.3 cells/mm2). Additionally, the ratio between the number of TIL and non-TIL was greater in PL (0.31) compared to that of LM (0.26). A similar trend appeared for Helper T cells and regulatory T cells (Treg), as PL consisted of higher numbers of T cells (791.8 Helper T cells/mm2, 195.7 Treg/mm2) than LM (626.3 Helper T cells/mm2, 121.3 Treg/mm2). However, cytotoxic T cells exhibiting GZB+ and CTLA-4- were fewer in PL (140.2 cells/mm2) than in LM (203.3 cells/mm2), and the ratio is 0.69. The mean number of GZB+ TIL in PL (32.5 cells/mm2) was lower than in LM (35.3 cells/mm2), and their proportions among total TIL counts were 0.12 and 0.31, respectively. In PL, GZB+: GZB- ratio is 0.16 while the ratio is 1.91 for LM. A fewer number of TILs exhibiting GZB suggests that PL has lower efficiency in immune response than LM. Another crucial checkpoint receptor that inhibits immune response, CTLA-4, was more prevalent in PL, with CTLA-4+: CTLA-4- ratio in Treg being 0.36 in PL, compared to 0.11 in LM. The tumor proportion score (TPS) of PD-L1 was higher in PL than LM (40.0 vs. 6.6).ConclusionsIn our study, we showed the differences in the numbers of TIL or regulatory T cells and expressions of immune checkpoint receptors (PD-L1, CTLA-4), which significantly influence outcomes for CIT. The study is ongoing to confirm different IME between the PL and LM groups in a larger tumor cohort.ReferencesPeng, Jianhong, et al., Immune Cell Infiltration in the Microenvironment of Liver Oligometastasis from Colorectal Cancer: Intratumoural CD8/CD3 Ratio Is a Valuable Prognostic Index for Patients Undergoing Liver Metastasectomy. Cancers 2019 Dec; 11(12): 1922. https://doi.org/10.3390/cancers11121922Tumeh, Paul C., et al., Liver Metastasis and treatment outcome with Anti-PD-1 monoclonal antibody in patients with melanoma and NSCLC. Cancer Immunol Res 2017 May; 5(5): 417–424. doi: 10.1158/2326-6066.CIR-16-0325Parra, E.R., Immune Cell Profiling in Cancer Using Multiplex Immunofluorescence and Digital Analysis Approaches; Streckfus, C.F., Ed.; IntechOpen: London, UK, 2018; pp. 1–13. doi: 10.5772/intechopen.80380Ribas, A., Hu-Lieskovan, S., What does PD-L1 positive or negative mean?. The Journal of Experimental Medicine 2016;213(13):2835–2840. https://doi.org/10.1084/jem.20161462

scholarly journals 3O A pre-existing inflammatory immune microenvironment predicts the clinical and immunological response of vulvar high-grade squamous intraepithelial lesions to therapeutic HPV16 peptide vaccination

2019 ◽  
Vol 30 (Supplement_11) ◽  
Author(s):  
Z Abdulrahman ◽  
N F C C de Miranda ◽  
M I E van Poelgeest ◽  
S H van der Burg
Keyword(s):  
T Cells ◽  
Clinical Response ◽  
Cd8 T Cells ◽  
Multispectral Imaging ◽  
Imaging System ◽  
Conflicts Of Interest ◽  
Human Papilloma Virus Type ◽  
Therapeutic Vaccination ◽  
High Grade ◽  
Immune Microenvironment

Abstract Background Vulvar High-grade Squamous Intraepithelial Lesion (vHSIL) is predominantly induced by high-risk Human Papilloma Virus type 16 (HPV16). In two independent trials, therapeutic vaccination against the oncoproteins of HPV16 with synthetic long peptides (SLP) resulted in vHSIL regression in about half of the patients after 12 months. Several studies have shown that the immune microenvironment influences therapy outcome. Therefore, a thorough investigation of the vHSIL immune microenvironment before and after SLP vaccination was performed, and its impact on clinical response was studied. Methods Two novel multiplex immunofluorescence panels were designed for formalin-fixed paraffin-embedded tissue, one for T cells (CD3, CD8, FoxP3, Tim3, Tbet, PD-1, DAPI) and one for myeloid cells (CD14, CD33, CD68, CD163, CD11c, PD-L1, DAPI). Pre- and 3 months post-vaccination biopsies of 29 patients and 27 healthy vulva excisions were stained, scanned with the Vectra multispectral imaging system, and automatically phenotyped and counted with inForm advanced image analysis software. Results A pre-existing pro-inflammatory TME, marked by high numbers of CD4 and CD8 T cells expressing Tbet and/or PD-1 as well as CD14+ inflammatory macrophages, is a strong predictor for good clinical response. A clear stepwise increase in pre-vaccination infiltrating Tbet+, CD4+, CD8+ T cells and CD14+ macrophages, and decrease in Foxp3+ Tregs was observed as response increased from non to partial to complete response. Moreover, the pre-vaccination immune microenvironment of complete responders resembled healthy vulva. Vaccination further increased infiltrating CD4+ and Tbet+ T cells and CD14+ macrophages and decreased FoxP3+ Tregs in the complete and partial responders, but not in the non responders. Conclusion Clinical responsiveness to therapeutic HPV16 SLP vaccination requires a pre-existing inflamed type 1 immune contexture in vHSIL. Hence, only patients with an inflamed TME should be selected for monotherapy by therapeutic vaccination, since this strategy is incapable of creating an inflamed TME in patients where this is absent. Legal entity responsible for the study The authors. Funding Leiden University Medical Center. Disclosure S.H. van der Burg: Advisory / Consultancy: ISA Pharmaceuticals. All other authors have declared no conflicts of interest.

Immune Cell Profiling in CML Bone Marrow By Multiplex Immunohistochemistry

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1897-1897
Author(s):  
Brück Oscar ◽  
Sami Blom ◽  
Riku Turkki ◽  
Panu E Kovanen ◽  
Antonio Ribeiro ◽  
...  
Keyword(s):  
T Cells ◽  
Cd8 T Cells ◽  
Immune Checkpoint ◽  
Cd4 T Cells ◽  
Research Funding ◽  
Immune Cell ◽  
Checkpoint Inhibitors ◽  
Cytotoxic T Cells ◽  
Helper T Cells ◽  
Analysis Software

Abstract Background In most solid tumors, CD8+ cytotoxic T-cells and type 1 T-helper cells are associated with a positive prognosis, but a strong immunosuppressive microenvironment may hamper their effectiveness. This notion has contributed to the development of new immune-activating therapies, such as immune checkpoint inhibitors. Although having demonstrated long-term remissions in many different solid tumor types, immune checkpoint inhibitors have not been evaluated comprehensively in hematological malignancies. In this study, we aimed to characterize the cellular and molecular immunological profiles of chronic myeloid leukemia (CML) patients' bone marrow (BM) samples. Methods BM biopsies were taken at the time of diagnosis from chronic phase CML patients (n=57) treated in the Helsinki University Hospital during years 2005-2015. We used non-leukemic (NL) BM biopsies (n=10) as controls. Using hematopathologic expertise, we constructed tissue microarray (TMA) blocks from duplicate BM spots characterized with high leukemic cell infiltration. We stained TMA slides using multiplexed immunohistochemistry (IHC) combining fluorescent and chromogenic staining allowing detection of up to six markers and nuclei simultaneously. Marker panels included T and B-lymphoid (CD3, CD4, CD8, CD20), myeloid dendritic (CD11c, BDCA-1, BDCA-3), macrophage (CD68, pSTAT1, c-MAF), natural killer cell (CD3 and CD56) and leukemia cell (CD34) markers. In addition, we examined immune checkpoint molecules (PD1, CTLA4, OX40, LAG3, TIM3) and their ligands in leukemic cells (HLA-G, PD-L1, PD-L2, HLA-ABC), as well as activation markers (CD25, CD27, CD57, Granzyme B and CD45RO). We analyzed leukemia patients' immune checkpoint expression profiles quantitatively using the image analysis software Cell Profiler and cell analysis software FlowJo and compared results with NL BMs' immune cell profiles. Results The proportion of CD3+ T cells of all cells was significantly higher in CML BM vs. NL BM (median 6.0% [interquartile range (IQR) 3.6-10.7] vs. 2.1% [IQR 1.5-4.5], p=0.001). There was no significant difference in CD8+ cytotoxic T cell levels, but CD4+ helper T cells were 8-fold more abundant in CML as compared to non-leukemic BM (p<0.0001). The proportion of both memory CD45RO+CD8+ T cells (62.2% [IQR 47.4-69.8] vs. 47.3% [IQR 27.9-56.2] of CD8+ T cells, p=0.03) and memory CD45RO+CD4+ T cells (61.8% [IQR 51.8-68.5] vs. 40.0% [IQR 25.6-57.9] of CD4+ T cells, p=0.004) were significantly higher in leukemic patients. Although the proportion of PD1+CD8+ T cells did not differ between CML and NL BM, there was a significantly lower proportion of PD1+CD4+ T cells in CML BM vs. NL BM (25.1% [IQR 17.0-38.7] vs. 69.5% [IQR 50.7-77.9], p<0.0001). However, as the number of CD4+ T cells was increased in CML, the absolute number of CD4+PD1+ T cells of total cell population was 3-fold higher in CML BM than in NL BM (p=0.02). Both the proportion of OX40+CD4+ T cells (42.3% [IQR 28.7-51.6] vs. 18.1% [IQR 13.2-22.9], p=0.001) and OX40+CD8+ T cells (42.6% [IQR 25.8-60.7] vs. 12.7% [IQR 5.0-15.8], p<0.0001) were increased in leukemic patients. Interestingly, also the proportion of OX40+PD1+CD8+ T cells (25.7% [IQR 15.4-36.4] vs. 11.9% [IQR 5.0-15.8], p=0.0019) was higher in CML samples. Conclusion Multiplex IHC allows detailed characterization of immune cell subtypes and their phenotypes in BM biopsy samples. Our data show significant heterogeneity in immune cell subsets between individual patients. The CML BM is characterized with an increase in CD3+ T cells, especially helper T cells and CD45RO+ memory T cells, when compared to non-leukemic BM. Phenotypically, OX40+PD1neg T cells and OX40+PD1+ cytotoxic T cells were elevated in CML patients. The analysis of other immune cell subclasses, including inhibitory immune cells, and the correlation of histologic findings to prognostic data are ongoing. Together, they will provide a detailed understanding of BM immune cell composition in CML. Disclosures Mustjoki: Novartis: Honoraria, Research Funding; Ariad: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding.

scholarly journals Altered Spatial Composition of the Immune Cell Repertoire in Association to CD34+ Blasts in Myelodysplastic Syndromes and Secondary Acute Myeloid Leukemia

Cancers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 186
Author(s):  
Marcus Bauer ◽  
Christoforos Vaxevanis ◽  
Haifa Kathrin Al-Ali ◽  
Nadja Jaekel ◽  
Christin Le Hoa Naumann ◽  
...  
Keyword(s):  
T Cells ◽  
Acute Myeloid Leukemia ◽  
Myelodysplastic Syndromes ◽  
Myeloid Leukemia ◽  
Multispectral Imaging ◽  
Immune Cell ◽  
Genetic Alterations ◽  
Spatial Proximity ◽  
Secondary Acute Myeloid Leukemia ◽  
Acute Myeloid

Background: Myelodysplastic syndromes (MDS) are caused by a stem cell failure and often include a dysfunction of the immune system. However, the relationship between spatial immune cell distribution within the bone marrow (BM), in relation to genetic features and the course of disease has not been analyzed in detail. Methods: Histotopography of immune cell subpopulations and their spatial distribution to CD34+ hematopoietic cells was determined by multispectral imaging (MSI) in 147 BM biopsies (BMB) from patients with MDS, secondary acute myeloid leukemia (sAML), and controls. Results: In MDS and sAML samples, a high inter-tumoral immune cell heterogeneity in spatial proximity to CD34+ blasts was found that was independent of genetic alterations, but correlated to blast counts. In controls, no CD8+ and FOXP3+ T cells and only single MUM1p+ B/plasma cells were detected in an area of ≤10 μm to CD34+ HSPC. Conclusions: CD8+ and FOXP3+ T cells are regularly seen in the 10 μm area around CD34+ blasts in MDS/sAML regardless of the course of the disease but lack in the surrounding of CD34+ HSPC in control samples. In addition, the frequencies of immune cell subsets in MDS and sAML BMB differ when compared to control BMB providing novel insights in immune deregulation.

scholarly journals Characterizing the Tumor Immune Microenvironment with Tyramide-Based Multiplex Immunofluorescence

2020 ◽  
Vol 25 (4) ◽  
pp. 417-432
Author(s):  
Hidetoshi Mori ◽  
Jennifer Bolen ◽  
Louis Schuetter ◽  
Pierre Massion ◽  
Clifford C. Hoyt ◽  
...  
Keyword(s):  
Tumor Microenvironment ◽  
Multispectral Imaging ◽  
Imaging System ◽  
Predictive Biomarkers ◽  
Cell Types ◽  
Immune Microenvironment ◽  
Tumor Immune Microenvironment ◽  
Manual Processing ◽  
Cell Densities ◽  
Immune Profiling

AbstractMultiplex immunofluorescence (mIF) allows simultaneous antibody-based detection of multiple markers with a nuclear counterstain on a single tissue section. Recent studies have demonstrated that mIF is becoming an important tool for immune profiling the tumor microenvironment, further advancing our understanding of the interplay between cancer and the immune system, and identifying predictive biomarkers of response to immunotherapy. Expediting mIF discoveries is leading to improved diagnostic panels, whereas it is important that mIF protocols be standardized to facilitate their transition into clinical use. Manual processing of sections for mIF is time consuming and a potential source of variability across numerous samples. To increase reproducibility and throughput we demonstrate the use of an automated slide stainer for mIF incorporating tyramide signal amplification (TSA). We describe two panels aimed at characterizing the tumor immune microenvironment. Panel 1 included CD3, CD20, CD117, FOXP3, Ki67, pancytokeratins (CK), and DAPI, and Panel 2 included CD3, CD8, CD68, PD-1, PD-L1, CK, and DAPI. Primary antibodies were first tested by standard immunohistochemistry and single-plex IF, then multiplex panels were developed and images were obtained using a Vectra 3.0 multispectral imaging system. Various methods for image analysis (identifying cell types, determining cell densities, characterizing cell-cell associations) are outlined. These mIF protocols will be invaluable tools for immune profiling the tumor microenvironment.

6 Murine T cell subsets and interleukins: Relationships between cytotoxic T cells, helper T cells and accessory cells

1982 ◽  
Vol 11 (3) ◽  
pp. 607-630
Author(s):  
Hermann Wagner ◽  
Martin Kronke ◽  
Werner Solbach ◽  
Peter Scheurich ◽  
Martin Röllinghoff ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cytotoxic T Cells ◽  
T Cell Subsets ◽  
Helper T Cells ◽  
Accessory Cells

scholarly journals Spatial Profiles of Intratumoral PD-1+ Helper T Cells Predict Prognosis in Head and Neck Squamous Cell Carcinoma

2021 ◽  
Vol 12 ◽  
Author(s):  
Kanako Yoshimura ◽  
Takahiro Tsujikawa ◽  
Junichi Mitsuda ◽  
Hiroshi Ogi ◽  
Sumiyo Saburi ◽  
...  
Keyword(s):  
Squamous Cell Carcinoma ◽  
T Cells ◽  
Tumor Cell ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Immune Cells ◽  
High Density ◽  
Helper T Cells ◽  
Tissue Segmentation ◽  
Immune Microenvironment

BackgroundFunctional interactions between immune cells and neoplastic cells in the tumor immune microenvironment have been actively pursued for both biomarker discovery for patient stratification, as well as therapeutic anti-cancer targets to improve clinical outcomes. Although accumulating evidence indicates that intratumoral infiltration of immune cells has prognostic significance, limited information is available on the spatial infiltration patterns of immune cells within intratumoral regions. This study aimed to understand the intratumoral heterogeneity and spatial distribution of immune cell infiltrates associated with cell phenotypes and prognosis in head and neck squamous cell carcinoma (HNSCC).MethodsA total of 88 specimens of oropharyngeal squamous cell carcinoma, categorized into discovery (n = 38) and validation cohorts (n = 51), were analyzed for immune contexture by multiplexed immunohistochemistry (IHC) and image cytometry-based quantification. Tissue segmentation was performed according to a mathematical morphological approach using neoplastic cell IHC images to dissect intratumoral regions into tumor cell nests versus intratumoral stroma.ResultsTissue segmentation revealed heterogeneity in intratumoral T cells, varying from tumor cell nest-polarized to intratumoral stroma-polarized distributions. Leukocyte composition analysis revealed higher ratios of TH1/TH2 in tumor cell nests with higher percentages of helper T cells, B cells, and CD66b+ granulocytes within intratumoral stroma. A discovery and validation approach revealed a high density of programmed death receptor-1 (PD-1)+ helper T cells in tumor cell nests as a negative prognostic factor for short overall survival. CD163+ tumor-associated macrophages (TAM) provided the strongest correlation with PD-1+ helper T cells, and cases with a high density of PD-1+ helper T cells and CD163+ TAM had a significantly shorter overall survival than other cases.ConclusionThis study reveals the significance of analyzing intratumoral cell nests and reports that an immune microenvironment with a high density of PD-1+ helper T cells in tumoral cell nests is a poor prognostic factor for HNSCC.

scholarly journals The Role of T Cells and Macrophages in Asthma Pathogenesis: A New Perspective on Mutual Crosstalk

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Xueyi Zhu ◽  
Jie Cui ◽  
La Yi ◽  
Jingjing Qin ◽  
Wuniqiemu Tulake ◽  
...  
Keyword(s):  
T Cells ◽  
Cell Activation ◽  
Immune Cell ◽  
Immune Microenvironment ◽  
Innate And Adaptive Immunity ◽  
Immune Cell Activation ◽  
Inflammatory Signals ◽  
Macrophage Dysfunction ◽  
New Perspective

Asthma is associated with innate and adaptive immunity mediated by immune cells. T cell or macrophage dysfunction plays a particularly significant role in asthma pathogenesis. Furthermore, crosstalk between them continuously transmits proinflammatory or anti-inflammatory signals, causing the immune cell activation or repression in the immune response. Consequently, the imbalanced immune microenvironment is the major cause of the exacerbation of asthma. Here, we discuss the role of T cells, macrophages, and their interactions in asthma pathogenesis.

scholarly journals Differential immune cell infiltrations between healthy periodontal and chronic periodontitis tissues

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Wei Li ◽  
Zheng Zhang ◽  
Zuo-min Wang
Keyword(s):  
T Cells ◽  
B Cells ◽  
Mast Cells ◽  
Plasma Cells ◽  
Immune Cell ◽  
Memory T Cells ◽  
Host Immunity ◽  
Memory B Cells ◽  
Helper T Cells ◽  
Follicular Helper

Abstract Background Host immunity plays an important role against oral microorganisms in periodontitis. Methods This study assessed the infiltrating immune cell subtypes in 133 healthy periodontal and 210 chronic periodontitis tissues from Gene Expression Omnibus (GEO) datasets using the CIBERSORT gene signature files. Results Plasma cells, naive B cells and neutrophils were all elevated in periodontitis tissues, when compared to those in healthy controls. In contrast, memory B cells, resting dendritic, mast cells and CD4 memory cells, as well as activated mast cells, M1 and M2 macrophages, and follicular helper T cells, were mainly present in healthy periodontal tissues. Furthermore, these periodontitis tissues generally contained a higher proportion of activated CD4 memory T cells, while the other subtypes of T cells, including resting CD4 memory T cells, CD8 T cells, follicular helper T cells (TFH) and regulatory T cells (Tregs), were relatively lower in periodontitis tissues, when compared to healthy tissues. The ratio of dendritic and mast cells and macrophages was lower in periodontitis tissues, when compared to healthy tissues. In addition, there was a significant negative association of plasma cells with most of the other immune cells, such as plasma cells vs. memory B cells (γ = − 0.84), plasma cells vs. resting dendritic cells (γ = − 0.64), plasma cells vs. resting CD4 memory T cells (γ = 0.50), plasma cells versus activated dendritic cells (γ = − 0.46), plasma cells versus TFH (γ = − 0.46), plasma cells versus macrophage M2 cells (γ = − 0.43), or plasma cells versus macrophage M1 cells (γ = − 0.40), between healthy control and periodontitis tissues. Conclusion Plasma cells, naive B cells and neutrophils were all elevated in periodontitis tissues. The infiltration of different immune cell subtypes in the periodontitis site could lead the host immunity against periodontitis.

scholarly journals Blockade of Lactate Dehydrogenase-A (LDH-A) Improves Efficacy of Anti-Programmed Cell Death-1 (PD-1) Therapy in Melanoma

Cancers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 450 ◽  
Author(s):  
Saeed Daneshmandi ◽  
Barbara Wegiel ◽  
Pankaj Seth
Keyword(s):  
T Cells ◽  
Cell Death ◽  
Lactate Dehydrogenase ◽  
Programmed Cell Death ◽  
Immune Cell ◽  
Cytotoxic T Cells ◽  
Treg Cells ◽  
Interferon Γ ◽  
Mitochondrial Activity ◽  
Small Subset

Immunotherapy is a curable treatment for certain cancers, but it is still only effective in a small subset of patients. We have recently reported that programmed cell death protein-1 (PD-1) ligand (PD-L1) expression is regulated by lactate present at high levels in the tumor microenvironment (TME). We hypothesized that the efficacy of anti-PD-1 treatment can be improved by blocking the lactate-generating enzyme, lactate dehydrogenase-A (LDH-A). Anti-PD-1 treatment of mice harboring LDH-A deficient B16-F10 melanoma tumors led to an increase in anti-tumor immune responses compared to mice implanted with tumors expressing LDH-A. Specifically, we observed heightened infiltration of natural killer (NK) cells and CD8+ cytotoxic T cells in the LDH-A deficient tumors. These infiltrated cytotoxic cells had an elevated production of interferon-γ (IFN-γ) and granzyme B. Mechanistically, CD8+ T cells isolated from the TME of LDH-A deficient B16-F10 melanoma tumors and treated with anti-PD-1 showed enhanced mitochondrial activity and increased reactive oxygen species (ROS) levels. Moreover, infiltration of T regulatory (Treg) cells was diminished in LDH-A deficient tumors treated with anti-PD-1. These altered immune cell profiles were clinically relevant as they were accompanied by significantly reduced tumor growth. Our study suggests that blocking LDH-A in the tumor might improve the efficacy of anti-PD-1 therapy.

scholarly journals Delayed Clearance of Ehrlichia chaffeensis Infection in CD4+ T-Cell Knockout Mice†

2004 ◽  
Vol 72 (1) ◽  
pp. 159-167 ◽  
Author(s):  
Roman R. Ganta ◽  
Chuanmin Cheng ◽  
Melinda J. Wilkerson ◽  
Stephen K. Chapes
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cytotoxic T Cells ◽  
Cell Activity ◽  
Helper T Cells ◽  
Cytotoxic T Cell ◽  
Mouse Strains ◽  
Cell Mediated Immunity ◽  
Ehrlichia Chaffeensis ◽  
Wild Type

ABSTRACT Human monocytic ehrlichiosis is an emerging tick-borne disease caused by the rickettsia Ehrlichia chaffeensis. To examine the role of helper T cells in host resistance to this macrophage-tropic bacterium, we assessed E. chaffeensis infections in three mouse strains with differing functional levels of helper T cells. Wild-type, C57BL/6J mice resolved infections in approximately 2 weeks. Major histocompatibility complex class II (MHCII) knockout, B6.129-Abb tm1 mice lacking helper T cells developed persistent infections that were not resolved even after several months. CD4+ T-cell-deficient, B6.129S6-Cd4 tm1Knw mice cleared the infection, but the clearance took 2 weeks longer than it did for wild-type mice. C57BL/6J mice resolved infection more rapidly following a second experimental challenge, but B6.129S6-Cd4 tm1Knw mice did not. The B6.129S6-Cd4 tm1Knw mice also developed active E. chaffeensis-specific immunoglobulin G responses that were slightly lower in concentration and slower to develop than that observed in C57BL/6J mice. E. chaffeensis-specific cytotoxic T cells were not detected following a single bacterial challenge in any mouse strain, including wild-type C57BL/6J mice. However, the cytotoxic T-cell activity developed in all three mouse strains, including the MHCII and CD4+ T-cell knockouts, when challenged with a second E. chaffeensis infection. The data reported here suggest that the cell-mediated immunity, orchestrated by CD4+ T cells is critical for conferring rapid clearance of E. chaffeensis.

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