Consequences of Aryl hydrocarbon receptor activation in dendritic cells

TCDD (dioxin) causes immunosuppression via activation of the Aryl hydrocarbon receptor (AhR). Dendritic cells (DCs), the professional antigen-presenting cells in the immune system, are adversely affected by TCDD. However, limited information exists regarding the effects of AhR activation on DCs. We evaluated the consequences of AhR activation by TCDD on both steady-state and inflammatory DCs using in vivo and in vitro approaches, respectively. We hypothesized that AhR activation alters DC homeostasis and differentiation leading to generation of immunosuppression. C57Bl/6 mice gavaged with an immunosuppressive dose of TCDD (15 ug/kg) displayed decreased frequency and number of splenic CD11chigh DCs on day 7. Moreover, TCDD induced a selective loss of the CD11chighCD8á-33D1+ splenic DCs subset, specialized at activating CD4+ T cells, but not the regulatory CD11chighCD8á+DEC205+ splenic DCs. Additionally, TCDD increased the expression of CD86 and CD54, while decreasing the frequency of CD11a and MHC II on the splenic CD11chigh DCs. Although TCDD did not alter the number and frequency of CD11clow splenic DCs, it decreased their MHC II and CD11a expression. The loss of CD11chigh DC was independent of an apoptotic event but involved a CCR7-mediated migratory event. Popliteal and brachial lymph node (PBLNs) CD11c+ cells displayed elevated levels of MHC II and CD40, but not DC loss following TCDD exposure. To examine the effects of TCDD on inflammatory DCs, BMDCs were generated in the presence of GM-CSF and vehicle or TCDD. TCDD decreased CD11c expression but increased MHC II, CD86 and CD25 expression on these BMDCs. These effects were AhR-dependent but not exclusively DRE-mediated. Additionally, TCDD modulated antigen uptake and increased LPS- and CpG-induced IL-6 and TNF-á levels but decreased nitric oxide production by the BMDCs. TCDD downregulated LPS- and CpG-induced p65 levels and induced a trend towards upregulation of RelB levels in BMDCs. Despite the induction of suppressive mediators IDO1, IDO2 and TGFâ3, TCDD-BMDCs failed to suppress T cell activation in vivo or induce the generation of adaptive T-regs in vitro. Collectively, our data suggest that AhR activation disrupts DC homeostasis, modulates DC differentiation, TLR responsiveness and induces a regulatory phenotype, effects that may underlie TCDD-induced immunosuppression

Consequences of aryl hydrocarbon receptor activation in dendritic cells

TCDD (dioxin) causes immunosuppression via activation of the Aryl hydrocarbon receptor (AhR). Dendritic cells (DCs), the professional antigen-presenting cells in the immune system, are adversely affected by TCDD. However, limited information exists regarding the effects of AhR activation on DCs. We evaluated the consequences of AhR activation by TCDD on both steady-state and inflammatory DCs using in vivo and in vitro approaches, respectively. We hypothesized that AhR activation alters DC homeostasis and differentiation leading to generation of immunosuppression. C57Bl/6 mice gavaged with an immunosuppressive dose of TCDD (15 &mgr;g/kg) displayed decreased frequency and number of splenic CD11chigh DCs on day 7. Moreover, TCDD induced a selective loss of the CD11chighCD8&agr;-33D1+ splenic DCs subset, specialized at activating CD4+ T cells, but not the regulatory CD11chighCD8&agr;+DEC205+ splenic DCs. Additionally, TCDD increased the expression of CD86 and CD54, while decreasing the frequency of CD11a and MHC II on the splenic CD11c high DCs. Although TCDD did not alter the number and frequency of CD11clow splenic DCs, it decreased their MHC II and CD11a expression. The loss of CD11chigh DC was independent of an apoptotic event but involved a CCR7-mediated migratory event. Popliteal and brachial lymph node (PBLNs) CD11c+ cells displayed elevated levels of MHC II and CD40, but not DC loss following TCDD exposure. To examine the effects of TCDD on inflammatory DCs, BMDCs were generated in the presence of GM-CSF and vehicle or TCDD. TCDD decreased CD11c expression but increased MHC II, CD86 and CD25 expression on these BMDCs. These effects were AhR-dependent but not exclusively DRE-mediated. Additionally, TCDD modulated antigen uptake and increased LPS- and CpG-induced IL-6 and TNF-&agr; levels but decreased nitric oxide production by the BMDCs. TCDD downregulated LPS- and CpG-induced p65 levels and induced a trend towards upregulation of RelB levels in BMDCs. Despite the induction of suppressive mediators IDO1, IDO2 and TGFβ3, TCDD-BMDCs failed to suppress T cell activation in vivo or induce the generation of adaptive T-regs in vitro. Collectively, our data suggest that AhR activation disrupts DC homeostasis, modulates DC differentiation, TLR responsiveness and induces a regulatory phenotype, effects that may underlie TCDD-induced immunosuppression

Effects of TCDD on the Fate of Naive Dendritic Cells

The environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), causes immune suppression via activation of the aryl hydrocarbon receptor. Dendritic cells (DCs), the professional antigen-presenting cells in the immune system, are adversely affected by TCDD. We hypothesized that TCDD alters DC homeostasis, resulting in a loss of DCs in naive mice. To test this hypothesis, C57Bl/6 mice were gavaged with either vehicle or an immunosuppressive dose of TCDD (15 μg/kg). TCDD exposure decreased the frequency and number of splenic CD11chigh DCs on day 7 when compared with vehicle-treated controls. TCDD increased the expression of CD86 and CD54, while decreasing the frequency of splenic CD11chigh DCs expressing CD11a and major histocompatibility complex (MHC) class II. Moreover, TCDD selectively decreased the CD11chighCD8α−33D1+ splenic DCs specialized at activating CD4+ T cells but did not affect the regulatory CD11chighCD8α+DEC205+ splenic DCs. TCDD did not alter the number or frequency of CD11clow splenic DCs but decreased their MHC class II and CD11a expression. Loss of splenic CD11chigh DCs was independent of Fas-mediated apoptosis and was not due to alterations in the numbers of common DC precursors in the bone marrow or their ability to generate steady-state DCs in vitro. Instead, increased CCR7 expression on CD11chigh DCs suggested involvement of a migratory event. Popliteal and brachial lymph node CD11c+ cells showed elevated levels of MHC class II and CD40 following TCDD exposure. Collectively, this study shows the presence of a TCDD-sensitive splenic DC subpopulation in naive mice, suggesting that TCDD may induce suppression of T-cell-mediated immunity by disrupting DC homeostasis

In multiple sclerosis, oligoclonal bands connect to peripheral B‐cell responses

ObjectiveTo determine to what extent oligoclonal band (OCB) specificities are clonally interrelated and to what degree they are associated with corresponding B-cell responses in the peripheral blood (PB) of multiple sclerosis (MS) patients.MethodsMass-spectrometric proteomic analysis of isoelectric focused (IEF) cerebrospinal fluid (CSF) immunoglobulin G (IgG) was used in combination with next-generation deep-immune repertoire sequencing of PB and CSF IgG heavy chain variable regions from MS patients.ResultsWe find evidence for ongoing stimulation and maturation to antibody-expressing B cells to occur primarily inside the central nervous system (CNS) compartment. B cells participating in OCB production can also be identified in PB; these cells appear to migrate across the blood-brain barrier and may also undergo further antigen stimulation in the periphery. In individual patients, different bands comprising OCBs are clonally related.InterpretationOur data provide a high-resolution molecular analysis of OCBs and strongly support the concept that OCBs are not merely the terminal result of a targeted immune response in MS but represent a component of active B cell immunity that is dynamically supported on both sides of the blood-brain barrier

In multiple sclerosis, oligoclonal bands connect to peripheral B-cell responses.

ObjectiveTo determine to what extent oligoclonal band (OCB) specificities are clonally interrelated and to what degree they are associated with corresponding B-cell responses in the peripheral blood (PB) of multiple sclerosis (MS) patients.MethodsMass-spectrometric proteomic analysis of isoelectric focused (IEF) cerebrospinal fluid (CSF) immunoglobulin G (IgG) was used in combination with next-generation deep-immune repertoire sequencing of PB and CSF IgG heavy chain variable regions from MS patients.ResultsWe find evidence for ongoing stimulation and maturation to antibody-expressing B cells to occur primarily inside the central nervous system (CNS) compartment. B cells participating in OCB production can also be identified in PB; these cells appear to migrate across the blood-brain barrier and may also undergo further antigen stimulation in the periphery. In individual patients, different bands comprising OCBs are clonally related.InterpretationOur data provide a high-resolution molecular analysis of OCBs and strongly support the concept that OCBs are not merely the terminal result of a targeted immune response in MS but represent a component of active B cell immunity that is dynamically supported on both sides of the blood-brain barrier

In multiple sclerosis, oligoclonal bands connect to peripheral B‐cell responses

OBJECTIVE: To determine to what extent oligoclonal band (OCB) specificities are clonally interrelated and to what degree they are associated with corresponding B-cell responses in the peripheral blood (PB) of multiple sclerosis (MS) patients. METHODS: Mass-spectrometric proteomic analysis of isoelectric focused (IEF) cerebrospinal fluid (CSF) immunoglobulin G (IgG) was used in combination with next-generation deep-immune repertoire sequencing of PB and CSF IgG heavy chain variable regions from MS patients. RESULTS: We find evidence for ongoing stimulation and maturation to antibody-expressing B cells to occur primarily inside the central nervous system (CNS) compartment. B cells participating in OCB production can also be identified in PB; these cells appear to migrate across the blood–brain barrier and may also undergo further antigen stimulation in the periphery. In individual patients, different bands comprising OCBs are clonally related. INTERPRETATION: Our data provide a high-resolution molecular analysis of OCBs and strongly support the concept that OCBs are not merely the terminal result of a targeted immune response in MS but represent a component of active B cell immunity that is dynamically supported on both sides of the blood-brain barrier

Immune inhibitory molecules LAG-3 and PD-1 synergistically regulate T-cell function to promote tumoral immune escape

Inhibitory receptors on immune cells are pivotal regulators of immune escape in cancer. Among these inhibitory receptors, CTLA-4 (targeted clinically by ipilimumab) serves as a dominant off-switch while other receptors such as PD-1 and LAG-3 seem to serve more subtle rheostat functions. However, the extent of synergy and cooperative interactions between inhibitory pathways in cancer remain largely unexplored. Here, we reveal extensive coexpression of PD-1 and LAG-3 on tumor-infiltrating CD4 + and CD8 + T cells in three distinct transplantable tumors. Dual anti-LAG-3/anti-PD-1 antibody treatment cured most mice of established tumors that were largely resistant to single antibody treatment. Despite minimal immunopathologic sequelae in PD-1 and LAG-3 single knockout mice, dual knockout mice abrogated self-tolerance with resultant autoimmune infiltrates in multiple organs, leading to eventual lethality. However, Lag3 -/-Pdcd1 -/- mice showed markedly increased survival from and clearance of multiple transplantable tumors. Together, these results define a strong synergy between the PD-1 and LAG-3 inhibitory pathways in tolerance to both self and tumor antigens. In addition, they argue strongly that dual blockade of these molecules represents a promising combinatorial strategy for cancer. ©2011 AACR