Response of rhesus monkey lymphocytes to short-term administration of THC

Four Rhesus monkeys were subjected to daily administration of 2.5 mg of tetrahydrocannabinol (THC)/kg body wt, after establishing the norms for complete blood count, T- and B-cell concentrations, and the dose response of thymidine incorporation after PHA stimulation. THC was administered daily for 3 weeks, the treatment was stopped, and then the animals were allowed to recover for 4 weeks. Cellular responses, incorporation studies and fibrinogen levels were determined during the treatment and recovery phases. Compared to 4 vehicle-treated animals, the THC-treated animals experienced significant augmentation of both their total white cell and their neutrophil counts during the recovery phase which returned to normal levels during the recovery phase. There was no alteration in total lymphocyte count or T- or B-cell concentrations. Fibrinogen levels of the THC-treated animals during the treatment phase were also elevated compared to controls, and the levels diminished to the same values as the vehicle-treated animals during recovery phase. Possible mechanisms for the response of Rhesus monkeys to short-term administration of THC are discussed.