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Polymicrobial Sepsis Chronic Immunoparalysis Is Defined by Diminished Ag-Specific T Cell-Dependent B Cell Responses.

ABSTRACT: Immunosuppression is one hallmark of sepsis, decreasing the host response to the primary septic pathogens and/or secondary nosocomial infections. CD4 T cells and B cells are among the array of immune cells that experience reductions in number and function during sepsis. "Help" from follicular helper (Tfh) CD4 T cells to B cells is needed for productive and protective humoral immunity, but there is a paucity of data defining the effect of sepsis on a primary CD4 T cell-dependent B cell response. Using the cecal ligation and puncture (CLP) mouse model of sepsis induction, we observed reduced antibody production in mice challenged with influenza A virus or TNP-KLH in alum early (2 days) and late (30 days) after CLP surgery compared to mice subjected to sham surgery. To better understand how these CD4 T cell-dependent B cell responses were altered by a septic event, we immunized mice with a Complete Freund's Adjuvant emulsion containing the MHC II-restricted peptide 2W1S_56-68 coupled to the fluorochrome phycoerythrin (PE). Immunization with 2W1S-PE/CFA results in T cell-dependent B cell activation, giving us the ability to track defined populations of antigen-specific CD4 T cells and B cells responding to the same immunogen in the same mouse. Compared to sham mice, differentiation and class switching in PE-specific B cells were blunted in mice subjected to CLP surgery. Similarly, mice subjected to CLP had reduced expansion of 2W1S-specific T cells and Tfh differentiation after immunization. Our data suggest CLP-induced sepsis impacts humoral immunity by affecting the number and function of both antigen-specific B cells and CD4 Tfh cells, further defining the period of chronic immunoparalysis after sepsis induction.

SUBMITTER: Sjaastad FV

PROVIDER: S-EPMC6220049 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Polymicrobial Sepsis Chronic Immunoparalysis Is Defined by Diminished Ag-Specific T Cell-Dependent B Cell Responses.

Sjaastad Frances V FV Condotta Stephanie A SA Kotov Jessica A JA Pape Kathryn A KA Dail Cody C Danahy Derek B DB Kucaba Tamara A TA Tygrett Lorraine T LT Murphy Katherine A KA Cabrera-Perez Javier J Waldschmidt Thomas J TJ Badovinac Vladimir P VP Griffith Thomas S TS

Frontiers in immunology 20181031

Immunosuppression is one hallmark of sepsis, decreasing the host response to the primary septic pathogens and/or secondary nosocomial infections. CD4 T cells and B cells are among the array of immune cells that experience reductions in number and function during sepsis. "Help" from follicular helper (Tfh) CD4 T cells to B cells is needed for productive and protective humoral immunity, but there is a paucity of data defining the effect of sepsis on a primary CD4 T cell-dependent B cell response. ...[more]

PMID: 30429857

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Project description:OBJECTIVES:Cell death in lymphatic organs, such as the spleen, is in part responsible for immunosuppression and contributes to mortality during sepsis. An early and noninvasive detection of lymphoid cell death could thus have significant clinical implications. Here, we tested in vivo imaging of lymphoid cell death using a near-infrared annexin V (AV-750). DESIGN:Animal study. SETTING:Laboratory investigation. SUBJECTS:C57BL/6J wild-type and toll-like receptor 3 knockout mice. INTERVENTIONS:Mild and severe polymicrobial sepsis was induced with cecum ligation and puncture. Serum cytokines and acute kidney injury markers were tested by immunoassay and quantitative reverse transcription-polymerase chain reaction, respectively. Sepsis-induced lymphoid cell death was detected by fluorescent AV-750 accumulation in the thorax and abdomen (in vivo), in isolated organs (ex vivo), and in isolated cells (flow cytometry). Caspase-3 cleavage/activity and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining were tested for apoptosis. MEASUREMENTS AND MAIN RESULTS:Severe sepsis induced marked apoptosis in the thymus, spleen, and liver as demonstrated by cleaved caspase-3 and an increase in caspase-3 activity and terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive cells. A significant increase in fluorescent AV-750 signal was seen in the thoracic and upper abdominal fields and associated with the severity of sepsis. The in vivo thoracic and abdominal AV-750 fluorescent signal was attributed to the thymus, liver, and spleen as determined by ex vivo imaging and highly correlated with the levels of cell death in thymocytes and splenocytes, respectively, as measured by flow cytometry. Compared with wild-type septic mice, toll-like receptor 3 septic mice had attenuated abdominal AV-750 fluorescent signal, reduced ex vivo fluorescence in the spleen, and decreased splenocyte cell death. CONCLUSIONS:In vivo AV-750 fluorescent imaging provides spatially resolved and organ-specific detection of lymphoid cell death during polymicrobial sepsis. The AV-750 fluorescent intensity in the thoracic and abdominal fields is associated with sepsis severity and well correlated with sepsis-induced cell death in the thymus and spleen, respectively.

Project description:The sepsis-induced cytokine storm leads to severe lymphopenia and reduced effector capacity of remaining/surviving cells. This results in a prolonged state of immunoparalysis, that contributes to enhanced morbidity/mortality of sepsis survivors upon secondary infection. The impact of sepsis on several lymphoid subsets has been characterized, yet its impact on NK-cells remains underappreciated-despite their critical role in controlling infection(s). Here, we observed numerical loss of NK-cells in multiple tissues after cecal-ligation-and-puncture (CLP)-induced sepsis. To elucidate the sepsis-induced lesions in surviving NK-cells, transcriptional profiles were evaluated and indicated changes consistent with impaired effector functionality. A corresponding deficit in NK-cell capacity to produce effector molecules following secondary infection and/or cytokine stimulation (IL-12,IL-18) further suggested a sepsis-induced NK-cell intrinsic impairment. To specifically probe NK-cell receptor-mediated function, the activating Ly49H receptor, that recognizes the murine cytomegalovirus (MCMV) m157 protein, served as a model receptor. Although relative expression of Ly49H receptor did not change, the number of Ly49H+ NK-cells in CLP hosts was reduced leading to impaired in vivo cytotoxicity and the capacity of NK-cells (on per-cell basis) to perform Ly49H-mediated degranulation, killing, and effector molecule production in vitro was also severely reduced. Mechanistically, Ly49H adaptor protein (DAP12) activation and clustering, assessed by TIRF microscopy, was compromised. This was further associated with diminished AKT phosphorylation and capacity to flux calcium following receptor stimulation. Importantly, DAP12 overexpression in NK-cells restored Ly49H/D receptors-mediated effector functions in CLP hosts. Finally, as a consequence of sepsis-dependent numerical and functional lesions in Ly49H+ NK-cells, host capacity to control MCMV infection was significantly impaired. Importantly, IL-2 complex (IL-2c) therapy after CLP improved numbers but not a function of NK-cells leading to enhanced immunity to MCMV challenge. Thus, the sepsis-induced immunoparalysis state includes numerical and NK-cell-intrinsic functional impairments, an instructive notion for future studies aimed in restoring NK-cell immunity in sepsis survivors.

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Polymicrobial Sepsis Chronic Immunoparalysis Is Defined by Diminished Ag-Specific T Cell-Dependent B Cell Responses.

Publications

Polymicrobial Sepsis Chronic Immunoparalysis Is Defined by Diminished Ag-Specific T Cell-Dependent B Cell Responses.

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