The atypical chemokine receptor ACKR2 suppresses Th17 responses to protein autoantigens

Chemokine-directed leukocyte migration is a critical component of all innate and adaptive immune responses. The atypical chemokine receptor ACKR2 is expressed by lymphatic endothelial cells and scavenges pro-inflammatory CC chemokines to indirectly subdue leukocyte migration. This contributes to the resolution of acute inflammatory responses <i>in vivo</i>. ACKR2 is also universally expressed by innate-like B cells, suppressing their responsiveness to the non-ACKR2 ligand CXCL13, and controlling their distribution <i>in vivo</i>. The role of ACKR2 in autoimmunity remains relatively unexplored, although <i>Ackr2</i> deficiency reportedly lessens the clinical symptoms of experimental autoimmune encephalomyelitis induced by immunization with encephalogenic peptide (MOG<sub>35–55</sub>). This was attributed to poor T-cell priming stemming from the defective departure of dendritic cells from the site of immunization. However, we report here that <i>Ackr2</i>-deficient mice, on two separate genetic backgrounds, are not less susceptible to autoimmunity induced by immunization, and in some cases develop enhanced clinical symptoms. Moreover, ACKR2 deficiency does not suppress T-cell priming in response to encephalogenic peptide (MOG<sub>35–55</sub>), and responses to protein antigen (collagen or MOG<sub>1–125</sub>) are characterized by elevated interleukin-17 production. Interestingly, after immunization with protein, but not peptide, antigen, <i>Ackr2</i> deficiency was also associated with an increase in lymph node B cells expressing granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that enhances T helper type 17 (Th17) cell development and survival. Thus, <i>Ackr2</i> deficiency does not suppress autoreactive T-cell priming and autoimmune pathology, but can enhance T-cell polarization toward Th17 cells and increase the abundance of GM-CSF<sup>+</sup> B cells in lymph nodes draining the site of immunization

The atypical chemokine receptor ACKR2 suppresses Th17 responses to protein autoantigens

Chemokine-directed leukocyte migration is a critical component of all innate and adaptive immune responses. The atypical chemokine receptor ACKR2 is expressed by lymphatic endothelial cells and scavenges pro-inflammatory CC chemokines to indirectly subdue leukocyte migration. This contributes to the resolution of acute inflammatory responses <i>in vivo</i>. ACKR2 is also universally expressed by innate-like B cells, suppressing their responsiveness to the non-ACKR2 ligand CXCL13, and controlling their distribution <i>in vivo</i>. The role of ACKR2 in autoimmunity remains relatively unexplored, although <i>Ackr2</i> deficiency reportedly lessens the clinical symptoms of experimental autoimmune encephalomyelitis induced by immunization with encephalogenic peptide (MOG<sub>35–55</sub>). This was attributed to poor T-cell priming stemming from the defective departure of dendritic cells from the site of immunization. However, we report here that <i>Ackr2</i>-deficient mice, on two separate genetic backgrounds, are not less susceptible to autoimmunity induced by immunization, and in some cases develop enhanced clinical symptoms. Moreover, ACKR2 deficiency does not suppress T-cell priming in response to encephalogenic peptide (MOG<sub>35–55</sub>), and responses to protein antigen (collagen or MOG<sub>1–125</sub>) are characterized by elevated interleukin-17 production. Interestingly, after immunization with protein, but not peptide, antigen, <i>Ackr2</i> deficiency was also associated with an increase in lymph node B cells expressing granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that enhances T helper type 17 (Th17) cell development and survival. Thus, <i>Ackr2</i> deficiency does not suppress autoreactive T-cell priming and autoimmune pathology, but can enhance T-cell polarization toward Th17 cells and increase the abundance of GM-CSF<sup>+</sup> B cells in lymph nodes draining the site of immunization