Cannabinoid receptor type 2 (CB2) is one of the major receptors for cannabis, which is expressed all over the body especially on the immune-related cells. It is considered that CB2 can work as a regulator in the immune system, particularly to suppress inflammatory responses in macrophages and microglias when activated. However no other immune cells have been studied whether and how they get modulated by CB2 activity. The objective of this experiment is to search for the other immune cell that can be affected by CB2 activity, and reveal the detailed mechanism of CB2-involved immune regulation.
To characterize the CB2-regulated cells under the inflammatory state, we injected LPS (1 mg/kg, i.p.) to CB2 deficient mice (CB2-KO) and wild-type (WT) controls. Spleen has been harvested from these mice 2 hours after the LPS administration, and immunophenotyping by flow cytometry has been conducted. In this experiment, we found the particular increase of the type 2 classical dendritic cell (cDC2) population in LPS-treated CB2-KO. As past studies reported that cDC2 recruits helper T cells when the body is exposed to an allergen, we further induced allergic rhinitis by OVA sensitization to investigate in-vivo effect of cDC2 increase in CB2-KO and WT animals. As expected, CB2 deficiency resulted as the significant exacerbation of allergic symptoms compared to WT mice. These results suggest that CB2 activity may suppress the allergic response by the reduction of cDC2 recruitment. Pharmacological effect of CB2 agonists to these symptoms will be studied as the future experiment.