Does THC suppress the immune system?

THC has immunosuppressive effects, primarily mediated through CB2 receptors on immune cells. In vitro and animal studies show THC reduces T-cell proliferation, suppresses natural killer cell activity, inhibits macrophage function, and shifts cytokine profiles toward anti-inflammatory (Th2) patterns. In humans, chronic cannabis users show altered immune profiles, though the clinical significance is debated. For most healthy adults, these effects appear modest and reversible. However, for immunocompromised patients (HIV, transplant recipients, cancer patients on chemotherapy), the immunosuppressive effects may be clinically relevant. Paradoxically, this immunosuppression is also the basis for investigating cannabinoids in autoimmune conditions.