ABSTRACT
Early during Gram-negative sepsis, excessive release of pro-inflammatory cytokines can cause septic shock that is often followed by a state of immune paralysis characterized by the failure to mount adaptive immunity towards secondary microbial infections. Especially, the early mechanisms responsible for such immune hypo-responsiveness are unclear. Here, we show that TLR4 is the key immune sensing receptor to initiate paralysis of T-cell immunity after bacterial sepsis. Downstream of TLR4, signalling through TRIF but not MyD88 impaired the development of specific T-cell immunity against secondary infections. We identified type I interferon (IFN) released from splenic macrophages as the critical factor causing T-cell immune paralysis. Early during sepsis, type I IFN acted selectively on dendritic cells (DCs) by impairing antigen presentation and secretion of pro-inflammatory cytokines. Our results reveal a novel immune regulatory role for type I IFN in the initiation of septic immune paralysis, which is distinct from its well-known immune stimulatory effects. Moreover, we identify potential molecular targets for therapeutic intervention to overcome impairment of T-cell immunity after sepsis.
Subject(s)
Adaptive Immunity , Interferon Type I/metabolism , Macrophages/metabolism , Sepsis/immunology , Spleen/metabolism , Animals , Dendritic Cells/metabolism , Macrophages/pathology , Mice , Mice, Inbred C57BL , Myeloid Differentiation Factor 88/metabolism , Sepsis/metabolism , Signal Transduction , Toll-Like Receptor 4/metabolismABSTRACT
A key event in the successful induction of adaptive immune responses is the antigen-specific activation of T cells by dendritic cells (DCs). Although LFA-1 (lymphocyte function-associated antigen 1) on T cells is considered to be important for antigen-specific T-cell activation, the role for LFA-1 on DCs remains elusive. Using 2 different approaches to activate LFA-1 on DCs, either by deletion of the αL-integrin cytoplasmic GFFKR sequence or by silencing cytohesin-1-interacting protein, we now provide evidence that DCs are able to make use of active LFA-1 and can thereby control the contact duration with naive T cells. Enhanced duration of DC/T-cell interaction correlates inversely with antigen-specific T-cell proliferation, generation of T-helper 1 cells, and immune responses leading to delayed-type hypersensitivity. We could revert normal interaction time and T-cell proliferation to wild-type levels by inhibition of active LFA-1 on DCs. Our data further suggest that cytohesin-1-interacting protein might be responsible for controlling LFA-1 deactivation on mature DCs. In summary, our findings indicate that LFA-1 on DCs needs to be in an inactive state to ensure optimal T-cell activation and suggest that regulation of LFA-1 activity allows DCs to actively control antigen-driven T-cell proliferation and effective immune responses.
Subject(s)
Cell Communication/immunology , Dendritic Cells/immunology , Lymphocyte Function-Associated Antigen-1/immunology , T-Lymphocytes/immunology , Animals , Carrier Proteins/genetics , Carrier Proteins/metabolism , Cell Adhesion/immunology , Cell Proliferation , Cells, Cultured , Dendritic Cells/cytology , Dendritic Cells/metabolism , Flow Cytometry , Hypersensitivity, Delayed/immunology , Hypersensitivity, Delayed/metabolism , Intercellular Adhesion Molecule-1/immunology , Intercellular Adhesion Molecule-1/metabolism , Interleukin-2/genetics , Interleukin-2/metabolism , Lymphocyte Activation/immunology , Lymphocyte Function-Associated Antigen-1/genetics , Lymphocyte Function-Associated Antigen-1/metabolism , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , RNA Interference , Receptors, Antigen, T-Cell/genetics , Receptors, Antigen, T-Cell/metabolism , Reverse Transcriptase Polymerase Chain Reaction , T-Lymphocytes/cytology , T-Lymphocytes/metabolism , Th1 Cells/cytology , Th1 Cells/immunology , Th1 Cells/metabolism , Time FactorsABSTRACT
Leucocyte function-associated antigen-1 (LFA-1) is known to be involved in immune reactions leading to allograft rejection. The role of deactivating LFA-1 in this context has not been investigated yet, although it is accepted that regulating LFA-1 activity is essential for T-cell function. Expressing LFA-1 locked in an active state in mice (LFA-1(d/d)) allowed us to investigate the in vivo function of LFA-1 deactivation for allograft rejection in a model of heterotopic cardiac transplantation. We provide in vivo evidence that regulating LFA-1 activity from an active to an inactive state controls antigen-specific priming and proliferation of T cells in response to allogeneic stimuli. Consequently, defective LFA-1 deactivation significantly prolonged cardiac allograft survival. Furthermore, reduced numbers of alloantigen-specific T cells and non-allo-specific innate immune cells within allografts of LFA-1(d/d) recipients indicate that expression of active LFA-1 impairs inflammatory responses involving all major leucocyte subpopulations. Taken together, our in vivo data suggest that LFA-1 deactivation is important for the formation of inflammatory lesions and rejection of cardiac allografts. Thus, the dynamic regulation of LFA-1 activity, rather than the mere presence of LFA-1, appears to contribute to the control of immune reactions inducing allogeneic transplant rejection.
Subject(s)
Graft Rejection/immunology , Heart Transplantation , Lymphocyte Function-Associated Antigen-1/metabolism , T-Lymphocytes/metabolism , Animals , Cell Movement/genetics , Cell Movement/immunology , Cell Proliferation , Graft Rejection/genetics , Graft Rejection/metabolism , Graft Rejection/pathology , Graft Survival/genetics , Graft Survival/immunology , Lymphocyte Activation/genetics , Lymphocyte Activation/immunology , Lymphocyte Function-Associated Antigen-1/genetics , Lymphocyte Function-Associated Antigen-1/immunology , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Transgenic , T-Lymphocytes/immunology , T-Lymphocytes/pathologyABSTRACT
BACKGROUND: Pretransplant screening in living donor kidney transplantation includes human leukocyte antigen matching, and panel reactive antibody analysis, whereas T cell mediated anti-donor reactivity is not assessed routinely. We investigated T cell reactivity after living related kidney transplantation between two monocygotic twins and in consequence correlated the withdrawal of individual immunosuppressive medication with immunological findings. METHODS: Immunosuppression consisted of mycophenolate mofetil, glucocorticoid single shot, and induction therapy with antithymocyte immunoglobulin. RESULTS: FACS analysis of recipient peripheral blood cells revealed a normal haemogram after transplantation, showing non-activated CD4 and CD8 cells. Mixed lymphocyte reaction did not reveal donor-specific T cell activity. IFN-gamma and IL-10 ELISA of supernatants of recipient cells cocultivated with donor cells support the lack of Th1 and Th2 cell differentiation. CONCLUSION: Based on immunological findings on days 5 and 20 MMF-therapy was reduced and stopped. Immunological monitoring on day 90 confirmed the absence of immune reactions directed against donor tissue.