Production of endocannabinoids by activated T cells and B cells modulates inflammation associated with delayed-type hypersensitivity.

Endocannabinoids are endogenous ligands for the cannabinoid (CB) receptors which include anandamide (AEA) and 2-arachidonyl glycerol (2-AG). 2-AG has been linked to inflammation due to its elevated expression in animal models of autoimmunity and hypersensitivity. However, administration of exogenous 2-AG has been shown to suppress inflammation making its precise role unclear. In the current study, we investigated the role of 2-AG following immunization of C57BL/6 (BL6) mice with methylated BSA (mBSA) antigen, which triggers both delayed-type hypersensitivity (DTH) and antibody response. We found that while naïve T cells and B cells expressed low levels of 2-AG, expression significantly increased upon activation. Furthermore, mBSA-immunized mice exhibited higher 2-AG concentration than naïve mice. Exogenous 2-AG treatment (40 mg/kg) in mBSA-immunized mice led to reduced DTH response, and decreased Th1 and Th17-associated cytokines including IL-6, IL-2, TNF-α, and the IgG response. Addition of 2-AG to activated popliteal lymph node (PopLN) cell cultures also inhibited lymphocyte proliferation. Together, these data show for the first time that activated T and B cells produce 2-AG, which plays a negative regulatory role to decrease DTH via inhibition of T-cell activation and proliferation. Moreover, these findings suggest that exogenous 2-AG treatment can be used therapeutically in Th1- or Th17-driven disease.