Immune synapses between mast cells and γδ T cells limit viral infection
Chinmay Kumar Mantri, Ashley L. St. John
Chinmay Kumar Mantri, Ashley L. St. John
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Research Article Immunology Infectious disease

Immune synapses between mast cells and γδ T cells limit viral infection

Abstract

Mast cells (MCs) are immune sentinels, but whether they also function as antigen-presenting cells (APCs) remains elusive. Using mouse models of MC deficiency, we report on MC-dependent recruitment and activation of multiple T cell subsets to the skin and draining lymph nodes (DLNs) during dengue virus (DENV) infection. Newly recruited and locally proliferating γδ T cells were the first T cell subset to respond to MC-driven inflammation, and their production of IFN-γ was MC dependent. MC–γδ T cell conjugates were observed consistently in infected peripheral tissues, suggesting a new role for MCs as nonconventional APCs for γδ T cells. MC-dependent γδ T cell activation and proliferation during DENV infection required T cell receptor (TCR) signaling and the nonconventional antigen presentation molecule endothelial cell protein C receptor (EPCR) on MCs. γδ T cells, not previously implicated in DENV host defense, killed infected targeted DCs and contributed to the clearance of DENV in vivo. We believe immune synapse formation between MCs and γδ T cells is a novel mechanism to induce specific and protective immunity at sites of viral infection.

Authors

Chinmay Kumar Mantri, Ashley L. St. John

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Figure 5

MC-dependent recruitment and contact-dependent activation and proliferation of γδ T cells.

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MC-dependent recruitment and contact-dependent activation and proliferat...
(A) Schematic showing the initial cell locations and conditions for the Transwell assay for B–D. BMMCs or BMMΦ were infected with DENV in the lower chamber, and T cells (n = 3 mice) were added to the top chamber to analyze migration and activation of T cell subsets across the Transwell. (B) Significantly higher numbers of T cells migrated to the bottom chamber containing DENV2-stimulated MCs but not DENV2-infected BMMΦ. (C) Among the T cells that migrated to the lower chamber, the γδ T cell subset was enriched in a MC-dependent manner. (D) The ratio of activated γδ T cells (CD3+γδTCR+CD69+) in the lower versus upper chambers showed a significant increase in response to DENV2-stimulated MCs. (E) DENV2-stimulated expression of γδ T cell chemoattractants in MCs. (F) Intracellular staining for chemokines showed increased CXCL10 and CCL2 production by DENV-treated MCs 24 hours after challenge with DENV, as measured by flow cytometry. (G–I) Isolated T cells were cultured with BMMCs in the presence or absence of DENV to assess MC-dependent and DENV-dependent activation and proliferation. Cells were stained for CD3, CD4, CD8, CD69, and the γδ TCR and analyzed by flow cytometry after 96 hours of coculture. The percentages of total and activated (G) γδ, (H) CD4+, and (I) CD8+ T cells were compared. (J) T cells were labeled with CFSE prior to coculturing with BMMCs, and the percentage of proliferating γδ T cells was measured by flow cytometry. Representative flow cytometric plots are shown in Supplemental Figures 11 and 12. Data represent the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 2-way ANOVA with Tukey’s post test (B–E), Student’s unpaired, 2-tailed t test (F), and 1-way ANOVA with Tukey’s post test (G–J).