Loss of DAP12 and FcRγ Drives Exaggerated IL-12 Production and CD8+ T Cell Response by CCR2+ Mo-DCs

Abstract

Dap12 and FcRγ, the two transmembrane ITAM-containing signaling adaptors expressed in dendritic cells (DC), are implicated in the regulation of DC function. Several activating and adhesion receptors including integrins require these chains for their function in triggering downstream signaling and effector pathways, however the exact role(s) for Dap12 and FcRγ remains elusive as their loss can lead to both attenuating and enhancing effects. Here, we report that mice congenitally lacking both Dap12 and FcRγ chains (DF) show a massively enhanced effector CD8+ T cell response to protein antigen immunization or West Nile Virus (WNV) infection. Thus, immunization of DF mice with MHCI-restricted OVA peptide leads to accumulation of IL-12-producing monocyte-derived dendritic cells (Mo-DC) in draining lymph nodes, followed by vastly enhanced generation of antigen-specific IFNγ-producing CD8+ T cells. Moreover, DF mice show increased viral clearance in the WNV infection model. Depletion of CCR2+ monocytes/macrophages in vivo by administration anti-CCR2 antibodies or clodronate liposomes completely prevents the exaggerated CD8+ T cell response in DF mice. Mechanistically, we show that the loss of Dap12 and FcRγ-mediated signals in Mo-DC leads to a disruption of GM-CSF receptor-induced STAT5 activation resulting in upregulation of expression of IRF8, a transcription factor. Consequently, Dap12- and FcRγ-deficiency exacerbates GM-CSF-driven monocyte differentiation and production of inflammatory Mo-DC. Our data suggest a novel cross-talk between DC-ITAM and GM-CSF signaling pathways, which controls Mo-DC differentiation, IL-12 production, and CD8+ T cell responses.

Identification of TYROBP and C1QB as Two Novel Key Genes With Prognostic Value in Gastric Cancer by Network Analysis

“…Taken together, these results indicated that TYROBP might be playing an immunosuppressive role on CD8 + T cells and macrophages to promote tumor immune escape in gastric cancer. Coincidentally, Yoshida et al ( 53 ) reported that TYROBP deficiency in liver allografts resulted in activation of graft-infiltrating CD8 + T cells and production of pro-inflammatory cytokine, whereas Kovats et al ( 54 ) found that loss of TYROBP and FcRγ promoted IL-12 production and CD8 + T cell response by CCR2 + Mo-DCs. Thus, TYROBP might be a negative factor in anti-tumor immune response.…”

Age-Dependent Cell Trafficking Defects in Draining Lymph Nodes Impair Adaptive Immunity and Control of West Nile Virus Infection

“…Mice were injected subcutaneously in the footpad with an emulsion containing CFA and 10 nmoles of OVA 323–337 peptide, and DLN were analyzed at indicated time points. The ELISPOT assay has been described previously [ 50 , 51 ]. To evaluate MHC class II specific T cell responses in adult and old mice, 5 x 10 5 cells from the DLN were harvested at day 7 post-immunization and plated on 96-well plates with Immobilon-P membrane coated with anti-mouse IL-2 antibody.…”

“…To evaluate MHC class II specific T cell responses in adult and old mice, 5 x 10 5 cells from the DLN were harvested at day 7 post-immunization and plated on 96-well plates with Immobilon-P membrane coated with anti-mouse IL-2 antibody. After overnight incubation, plates were washed, incubated with a secondary antibody and developed as previously described [ 50 , 51 ]. Spots were analyzed on dedicated equipment and software (Cellular Technology Ltd along with Immunospot software Version 5.0.9) to calculate the total number of antigen-specific CD4 + T cells in DLN.…”

Constitutively Activated DAP12 Induces Functional Anti-Tumor Activation and Maturation of Human Monocyte-Derived DC

“…Future studies with our constructs should be made with analysis of pathways that could disrupt activation of anti-tumor responses into inhibitory/suppressive ones. Gmyrek et al, for instance, recently showed that loss of DAP12 along the FcR gamma leads to acute upregulation of cytokine responses [ 50 ] in some subtypes of myeloid cells. However, Mocsai et al showed similar results to ours shown that SYK activation was reduced in DAP12 −/− mice while the role of FcR gamma was only effective at reducing SYK when in combination with a reduction in DAP12 [ 51 ].…”