Dynamic CD4 T cell heterogeneity defines subset-specific suppression and PD-L1-blockade-driven functional restoration in chronic infection.

Inhibiting PD-1:PD-L1 signaling has transformed therapeutic immune restoration. CD4 T cells sustain immunity in chronic infections and cancer, yet little is known about how PD-1 signaling modulates CD4 helper T (T) cell responses or the ability to restore CD4 T-mediated immunity by checkpoint blockade. We demonstrate that PD-1:PD-L1 specifically suppressed CD4 T1 cell amplification, prevents CD4 T1 cytokine production and abolishes CD4 cytotoxic killing capacity during chronic infection in mice.

Early innate and adaptive immune perturbations determine long-term severity of chronic virus and Mycobacterium tuberculosis coinfection.

Chronic viral infections increase severity of Mycobacterium tuberculosis (Mtb) coinfection. Here, we examined how chronic viral infections alter the pulmonary microenvironment to foster coinfection and worsen disease severity. We developed a coordinated system of chronic virus and Mtb infection that induced central clinical manifestations of coinfection, including increased Mtb burden, extra-pulmonary dissemination, and heightened mortality.

A network of immune and microbial modifications underlies viral persistence in the gastrointestinal tract.

Many pathogens subvert intestinal immunity to persist within the gastrointestinal tract (GIT); yet, the underlying mechanisms that enable sanctuary specifically in this reservoir are unclear. Using mass cytometry and network analysis, we demonstrate that chronic LCMV infection of the GIT leads to dysregulated microbial composition, a cascade of metabolic alterations, increased susceptibility to GI disease, and a system-wide recalibration of immune composition that defines viral persistence. Chronic infection led to outgrowth of activated Tbet-expressing T reg cell populations unique to the GIT and the rapid erosion of pathogen-specific CD8 tissue-resident memory T cells.

GCN2 drives macrophage and MDSC function and immunosuppression in the tumor microenvironment.

General control nonderepressible 2 (GCN2) is an environmental sensor controlling transcription and translation in response to nutrient availability. Although GCN2 is a putative therapeutic target for immuno-oncology, its role in shaping the immune response to tumors is poorly understood. Here, we used mass cytometry, transcriptomics, and transcription factor-binding analysis to determine the functional impact of GCN2 on the myeloid phenotype and immune responses in melanoma.

Validation of CyTOF Against Flow Cytometry for Immunological Studies and Monitoring of Human Cancer Clinical Trials.

Flow cytometry is a widely applied approach for exploratory immune profiling and biomarker discovery in cancer and other diseases. However, flow cytometry is limited by the number of parameters that can be simultaneously analyzed, severely restricting its utility. Recently, the advent of mass cytometry (CyTOF) has enabled high dimensional and unbiased examination of the immune system, allowing simultaneous interrogation of a large number of parameters.

CD8 T Cell Priming in Established Chronic Viral Infection Preferentially Directs Differentiation of Memory-like Cells for Sustained Immunity.

CD8 T cell exhaustion impedes control of chronic viral infection; yet how new T cell responses are mounted during chronic infection is unclear. Unlike T cells primed at the onset of infection that rapidly differentiate into effectors and exhaust, we demonstrate that virus-specific CD8 T cells primed after establishment of chronic LCMV infection preferentially generate memory-like transcription factor TCF1 cells that were transcriptionally and proteomically distinct, less exhausted, and more responsive to immunotherapy. Mechanistically, adaptations of antigen-presenting cells and diminished T cell signaling intensity promoted differentiation of the memory-like subset at the expense of rapid effector cell differentiation, which was now highly dependent on IL-21-mediated CD4 T cell help for its functional generation.

Skin CD4(+) memory T cells exhibit combined cluster-mediated retention and equilibration with the circulation.

Although memory T cells within barrier tissues can persist as permanent residents, at least some exchange with blood. The extent to which this occurs is unclear. Here we show that memory CD4(+) T cells in mouse skin are in equilibrium with the circulation at steady state.

Limited Internodal Migration of T Follicular Helper Cells after Peripheral Infection with Herpes Simplex Virus-1.

The ability of CD4 T cells to give rise to specialized T follicular helper cells (TFH) critical to initiating appropriate Ab responses is regulated by environmental cues in lymphoid tissues draining the site of infection. In this study, we used a skin infection with HSV-1 characterized by the successive involvement of interconnected but distinct lymph nodes (LNs), to investigate the anatomical diversification of virus-specific CD4 T cell responses and the migratory capacity of TFH or their precursors. Whereas Th1 effector CD4 T cells expressing peripheral-targeting migration molecules readily migrated from primary to secondary reactive LNs, Bcl6(+) CXCR5(+) PD1(hi) TFH were largely retained at the site of initial activation with little spillover into the downstream LNs involved at later stages of infection.

Cutting edge: CD69 interference with sphingosine-1-phosphate receptor function regulates peripheral T cell retention.

Tissue-resident memory T cells provide local immune protection in barrier tissues, such as skin and mucosa. However, the molecular mechanisms controlling effector T cell retention and subsequent memory formation in those locations are not fully understood. In this study, we analyzed the role of CD69, an early leukocyte activation marker, in regulating effector T cell egress from peripheral tissues.

Distinct APC subtypes drive spatially segregated CD4+ and CD8+ T-cell effector activity during skin infection with HSV-1.

Efficient infection control requires potent T-cell responses at sites of pathogen replication. However, the regulation of T-cell effector function in situ remains poorly understood. Here, we show key differences in the regulation of effector activity between CD4+ and CD8+ T-cells during skin infection with HSV-1.