Δ9‐Tetrahydrocannabinol suppression of the primary immune response in rats

Abstract

The interaction of Δ⁹‐tetrahydrocannabinol (Δ⁹‐THC) with the primary immune response was investigated in female Fischer rats receiving sesame oil vehicle or Δ⁹‐THC in oral doses of 1, 5, or 10 mg/kg. Rats were given a single intraperitoneal injection of sheep red blood cells (SRBC) after, during, or before treatment with Δ⁹‐THC in order to evaluate the effect of the cannabinoid on the inductive and productive phases of the primary immune response to SRBC. At necropsy, body and spleen weights were recorded, sera were analyzed for antibody to SRBC by an hemagglutination method (HT), and splenic antibody forming cells (AFC) were determined by the localized hemolysis In gel plaque formation. Δ⁹‐THC inhibited the primary immune response by 33–44% at 10 mg/kg, suppressed the inductive phase by 48–78% at all doses, and impaired the productive phase by 26–59% at the higher doses. These results are the first direct demonstration of a Δ⁹‐THC‐induced immunosuppression of both phases of the primary immune response.