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Chem Phys Lipids. 2002 Dec 31;121(1-2):229-39.

Effects of delta-9-tetrahydrocannabinol on human immune function and host defense.

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Division of Pulmonary and Critical Care Medicine and Hematology/Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.


This review examines evidence that delta(9)-tetrahydrocannabinol (THC) can regulate and suppress human immune responses. Leukocytes express both cannabinoid receptor type 1 (CB1) and cannabinoid receptor type 2 (CB2), and levels of mRNA encoding for them are increased in peripheral blood leukocytes obtained from marijuana smokers, suggesting cannabinoid receptor activation in vivo. Exposure of human T-cells to THC suppresses their proliferation, inhibits the release of interferon-gamma, and skews the balance of T-helper cytokines towards a type 2 response. The majority of these effects are CB2 receptor-dependent. Consistent with an impact of THC on cell-mediated immunity, alveolar macrophages (AMs) recovered from the lungs of marijuana smokers are suppressed in their ability to release pro-inflammatory cytokines and nitric oxide (NO), and kill bacteria. Macrophage function is restored by treatment with interferon-gamma, a type 1 cytokine. Habitual exposure to THC appears capable of impacting on human cell-mediated immunity and host defense.

[Indexed for MEDLINE]

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