CX3CR1 Deficiency Attenuates DNFB-Induced Contact Hypersensitivity through Skewed Polarization towards M2 Phenotype in Macrophages

CX3CL1 can function as both an adhesion molecule and a chemokine for CX3CR1(+) cells, such as T cells, monocytes, and NK cells. Recent studies have demonstrated that CX3CL1–CX3CR1 interaction is associated with the development of various inflammatory skin diseases. In this study, we examined CX3CR1 involvement in 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity using CX3CR1(−/−) mice. Ear swelling and dermal edema were attenuated after DNFB challenge in CX3CR1(−/−) mice. Expression of TNF-α, IL-6, and M1 macrophage markers was decreased in the ears of CX3CR1(−/−) mice, whereas expression of M2 macrophage markers including arginase-1 was increased. Decreased TNF-α and IL-6 expression and increased arginase-1 expression were found in peritoneal macrophages from CX3CR1(−/−) mice. Furthermore, ear swelling was attenuated by depleting dermal macrophages in wild-type mice to a similar level to CX3CR1(−/−) mice. These results suggest that CX3CR1 deficiency could induce skewed polarization towards M2 phenotype in macrophages, resulting in attenuation of contact hypersensitivity response.