Expression of the CB1 cannabinoid receptor in macrophage-like cells from brain tissue: immunochemical characterization by fusion protein antibodies.

Antibodies designed to recognize a 74 amino acid sequence of the N- or C-terminal domain of the rat CB1 cannabinoid receptor detected a 58 kDa protein in immunoblots of brain and various cells known to express the CB1 cannabinoid receptor. A human B-lymphoblastoid cell line and macrophage-like cells from neonatal rat brain were also positive for CB1 receptor-like immunoreactivity. Immunocytochemical analysis performed with isolated Fab fragments showed surface staining in NG108-15 cells and brain macrophage like cells which also express MHC class II antigens. The data suggest a plausible role for CB1 receptors in the immune function of brain.