Project description:The extent to which tissue-specific viral infections generate memory T cells specifically adapted to and maintained within the target infection site is unknown. Here, we show that respiratory virus-specific memory T cells in mice and humans are generated and maintained in compartmentalized niches in lungs, distinct from populations in lymphoid tissue or circulation. Using a polyclonal mouse model of influenza infection combined with an in vivo antibody labeling approach and confocal imaging, we identify a spatially distinct niche in the lung where influenza-specific T-cell responses are expanded and maintained long term as tissue-resident memory (T(RM)) CD4 and CD8 T cells. Lung T(RM) are further distinguished from circulating memory subsets in lung and spleen based on CD69 expression and persistence independent of lymphoid stores. In humans, influenza-specific T cells are enriched within the lung T(RM) subset, whereas memory CD8 T cells specific for the systemic virus cytomegalovirus are distributed in both lung and spleen, suggesting that the site of infection affects T(RM) generation. Our findings reveal a precise spatial organization to virus-specific T-cell memory, determined by the site of the initial infection, with important implications for the development of targeted strategies to boost immunity at appropriate tissue sites.
Project description:T follicular helper (TFH) cells are crucial for B cell-mediated humoral immunity1. Although transcription factors such as BCL6 drive the differentiation of TFH cells2,3, it is unclear whether and how post-transcriptional and metabolic programs enforce TFH cell programming. Here we show that the cytidine diphosphate (CDP)-ethanolamine pathway co-ordinates the expression and localization of CXCR5 with the responses of TFH cells and humoral immunity. Using in vivo CRISPR-Cas9 screening and functional validation in mice, we identify ETNK1, PCYT2, and SELENOI-enzymes in the CDP-ethanolamine pathway for de novo synthesis of phosphatidylethanolamine (PE)-as selective post-transcriptional regulators of TFH cell differentiation that act by promoting the surface expression and functional effects of CXCR5. TFH cells exhibit unique lipid metabolic programs and PE is distributed to the outer layer of the plasma membrane, where it colocalizes with CXCR5. De novo synthesis of PE through the CDP-ethanolamine pathway co-ordinates these events to prevent the internalization and degradation of CXCR5. Genetic deletion of Pcyt2, but not of Pcyt1a (which mediates the CDP-choline pathway), in activated T cells impairs the differentiation of TFH cells, and this is associated with reduced humoral immune responses. Surface levels of PE and CXCR5 expression on B cells also depend on Pcyt2. Our results reveal that phospholipid metabolism orchestrates post-transcriptional mechanisms for TFH cell differentiation and humoral immunity, highlighting the metabolic control of context-dependent immune signalling and effector programs.
Project description:Sustained T cell receptor (TCR) stimulation is required for maintaining germinal center T follicular helper (GC-TFH) cells. Paradoxically, TCR activation induces interleukin-2 receptor (IL-2R) expression and IL-2 production, thereby initiating a feedback loop of IL-2 signaling that normally inhibits TFH cells. It is unclear how GC-TFH cells can receive prolonged TCR signaling without succumbing to the detrimental effects of IL-2. Using an influenza infection model, we show here that GC-TFH cells secreted large amounts of IL-2 but responded poorly to it. To maintain their IL-2 hyporesponsiveness, GC-TFH cells required intrinsic IL-6 signaling. Mechanistically, we found that IL-6 inhibited up-regulation of IL-2R? (CD122) by preventing association of STAT5 with the Il2rb locus, thus allowing GC-TFH cells to receive sustained TCR signaling and produce IL-2 without initiating a TCR/IL-2 inhibitory feedback loop. Collectively, our results identify a regulatory mechanism that controls the generation of GC-TFH cells.
Project description:Immunization in the absence of CD4(+) T cell help results in defective CD8(+) T cell memory, deficient recall responses and diminished protective immunity. Here we investigated at what stage during the immune response to pathogen CD4(+) T cells are essential in the promotion of functional CD8(+) T cell memory. Memory CD8(+) T cell numbers decreased gradually in the absence of CD4(+) T cells despite the presence of similar numbers of memory cell precursors at the peak of the effector phase. Adoptive transfer of effector or memory CD8(+) T cells into wild-type or CD4(+) T cell-deficient mice demonstrated that the presence of CD4(+) T cells was important only after, not during, the early CD8(+) T cell programming phase. In the absence of CD4(+) T cells, memory CD8(+) T cells became functionally impaired and decreased in quantity over time. We conclude that in the context of an acute infection, CD4(+) T cells are required only during the maintenance phase of long-lived memory CD8(+) T cells.
Project description:The transcriptional regulation underlying the differentiation of CD8(+) effector and memory T cells remains elusive. Here, we show that 18-month-old mice lacking the transcription factor Smad4 (homolog 4 of mothers against decapentaplegic, Drosophila), a key intracellular signaling effector for the TGF-β superfamily, in T cells exhibited lower percentages of CD44(hi)CD8(+) T cells. To explore the role of Smad4 in the activation/memory of CD8(+) T cells, 6- to 8-week-old mice with or without Smad4 in T cells were challenged with Listeria monocytogenes. Smad4 deficiency did not affect antigen-specific CD8(+) T-cell expansion but led to partially impaired cytotoxic function. Less short-lived effector T cells but more memory-precursor effector T cells were generated in the absence of Smad4. Despite that, Smad4 deficiency led to reduced memory CD8(+) T-cell responses. Further exploration revealed that the generation of central memory T cells was impaired in the absence of Smad4 and the cells showed survival issue. In mechanism, Smad4 deficiency led to aberrant transcriptional programs in antigen-specific CD8(+) T cells. These findings demonstrated an essential role of Smad4 in the control of effector and memory CD8(+) T-cell responses to infection.
Project description:The extent to which obesity compromises the differentiation and maintenance of protective memory CD8 T cell responses and renders obese individuals susceptible to infection remains unknown. In this study, we show that diet-induced obesity did not impact the maintenance of pre-existing memory CD8 T cells, including acquisition of a long-term memory phenotype (i.e., CD27(hi), CD62L(hi), KLRG1(lo)) and function (i.e., cytokine production, secondary expansion, and memory CD8 T cell-mediated protection). Additionally, obesity did not influence the differentiation and maintenance of newly evoked memory CD8 T cell responses in inbred and outbred hosts generated in response to different types of systemic (LCMV, L. monocytogenes) and/or localized (influenza virus) infections. Interestingly, the rate of naive-to-memory CD8 T cell differentiation after a peptide-coated dendritic cell immunization was similar in lean and obese hosts, suggesting that obesity-associated inflammation, unlike pathogen- or adjuvant-induced inflammation, did not influence the development of endogenous memory CD8 T cell responses. Therefore, our studies reveal that the obese environment does not influence the development or maintenance of memory CD8 T cell responses that are either primed before or after obesity is established, a surprising notion with important implications for future studies aiming to elucidate the role obesity plays in host susceptibility to infections.
Project description:IgG4-related disease (IgG4-RD) is a fibro-inflammatory disorder involving virtually every organ with a risk of organ dysfunction. Despite recent studies regarding B cell and T cell compartments, the disease's pathophysiology remains poorly understood. We examined and characterized subsets of circulating lymphocytes in untreated patients with active IgG4-RD. Twenty-eight consecutive patients with biopsy-proven IgG4-RD were included in a prospective, multicentric study. Lymphocytes' subsets were analyzed by flow cytometry, with analysis of TH1/TH2/TH17, TFH cells, and cytokine release by peripheral blood mononuclear cells. Results were compared to healthy controls and to patients with primary Sjögren's syndrome. Patients with IgG4-RD showed an increase of circulating T regulatory, TH2, TH17, and CD4+CXCR5+PD1+ TFH cell subsets. Accordingly, increased levels of IL-10 and IL-4 were measured in IgG-RD patients. TFH increase was characterized by the specific expansion of TFH2 (CCR6-CXCR3-), and to a lesser extent of TFH17 (CCR6+CXCR3-) cells. Interestingly, CD4+CXCR5+PD1+ TFH cells normalized under treatment. IgG4-RD is characterized by a shift of circulating T cells toward a TH2/TFH2 and TH17/TFH17 polarization. This immunological imbalance might be implicated in the disease's pathophysiology. Treatment regimens targeting such T cells warrant further evaluation.
Project description:Follicular helper T (TFH) cells control antibody responses by supporting antibody affinity maturation and memory formation. Inadequate TFH function has been found in individuals with ineffective responses to vaccines, but the mechanism underlying TFH regulation in vaccination is not understood. Here, we report that lower serum levels of the metabolic hormone leptin associate with reduced vaccine responses to influenza or hepatitis B virus vaccines in healthy populations. Leptin promotes mouse and human TFH differentiation and IL-21 production via STAT3 and mTOR pathways. Leptin receptor deficiency impairs TFH generation and antibody responses in immunisation and infection. Similarly, leptin deficiency induced by fasting reduces influenza vaccination-mediated protection for the subsequent infection challenge, which is mostly rescued by leptin replacement. Our results identify leptin as a regulator of TFH cell differentiation and function and indicate low levels of leptin as a risk factor for vaccine failure.
Project description:The mammalian target of rapamycin (mTOR) kinase is a critical regulator of the differentiation of helper and regulatory CD4+ T cells, as well as memory CD8+ T cells. In this study, we investigated the role of the ERK signaling pathway in regulating mTOR activation in T cells. We showed that activation of ERK following TCR engagement is required for sustained mTOR complex 1 (mTORC1) activation. Absence of kinase suppressor of Ras 1 (KSR1), a scaffold protein of the ERK signaling pathway, or inhibition of ERK resulted in decreased mTORC1 activity following T cell activation. However, KSR1-deficient mice displayed normal regulatory CD4+ T cell development, as well as normal memory CD8+ T cell responses to LCMV and Listeria monocytogenes infection. These data indicate that despite its role in mTORC1 activation, KSR1 is not required in vivo for mTOR-dependent T cell differentiation.
Project description:The germinal centre is a dynamic microenvironment in which B cells that express high-affinity antibody variants produced by somatic hypermutation are selected for clonal expansion by limiting the numbers of T follicular helper cells1,2. Although much is known about the mechanisms that control the selection of B cells in the germinal centre, far less is understood about the clonal behaviour of the T follicular helper cells that help to regulate this process. Here we report on the dynamic behaviour of T follicular helper cell clones during the germinal centre reaction. We find that, similar to germinal centre B cells, T follicular helper cells undergo antigen-dependent selection throughout the germinal centre reaction that results in differential proliferative expansion and contraction. Increasing the amount of antigen presented in the germinal centre leads to increased division of T follicular helper cells. Competition between T follicular helper cell clones is mediated by the affinity of T cell receptors for peptide-major-histocompatibility-complex ligands. T cells that preferentially expand in the germinal centre show increased expression of genes downstream of the T cell receptor, such as those required for metabolic reprogramming, cell division and cytokine production. These dynamic changes lead to marked remodelling of the functional T follicular helper cell repertoire during the germinal centre reaction.