CCR7 Expression of Intestinal Myeloid Cells and their Migratory Potential

Intestinal myeloid cells play an indispensable role in antigen sampling from the lumen and its transport to the mesenteric lymph nodes (mLN) where they prime naïve lymphocytes. CD103 and CX3CR1 expression distinguishes non-overlapping populations whose migratory potential is yet to be elucidated. Our group demonstrated that CD103⁺ DCs but not CX3CR1^hi cells migrate to the mLN via lymph (Schulz et al, 2009). In contrast, Diehl et al suggested that in microbiota-depleted mice, CX3CR1^hicells become migratory and enter into lymphatics and mLN in a CCR7-dependent manner (Diehl et al, 2013).

We therefore established a novel mouse model to monitor CCR7 expression and its regulation in-vivo. In this mouse model, insertion of GFP disrupts the function of CCR7 gene. Upon stimulation, cells from CCR7^GFP/GFP mice up-regulate CCR7/GFP but are not able to migrate because of the disrupted CCR7. In contrast, cells from CCR7^GFP/+ mice can up-regulate CCR7 and are capable of migrating to the draining LN. Mice were treated with antibiotics or left untreated and gavaged with R848 14 hours prior to analysis.

Upon R848 stimulation, intestinal CD103⁺and CD103^- DCs up-regulated CCR7/GFP, CD64⁺ macrophages didn’t express CCR7/GFP in CCR7^GFP/GFP mice even after dysbiosis induced by antibiotics. Moreover, in CX3CR1^GFP/+ mice, CX3CR1^intCD64^- but no CX3CR1^hiCD64⁺cells were found in the mLN after R848 treatment in both antibiotics-treated and-untreated mice.

Taken together, our data demonstrate that intestinal CD103⁺CX3CR1^- and CD103^-CXCR1^int DCs but not CD64⁺CX3CR1^hiresident macrophages up-regulate CCR7 and migrate to the mLN irrespective of the microbiota status of the mice.

+Contributed equally  *Contributed equally