Age-associated differences in cannabinoid-induced suppression of murine spleen, lymph node and thymus cell blastogenic responses.

The effects of delta 9-tetrahydrocannabinol (THC) and 11-OH THC on the proliferative responses of murine thymus, spleen and lymph node cells were examined. Specifically, weanling and adult mouse lymphocytes were stimulated in vitro with the T-cell mitogens concanavalin A and phytohemagglutinin. Thymus cells were suppressed at lower cannabinoid concentrations than cells from either spleen or lymph nodes. However, splenic cells from weanling mice were much more readily suppressed than were those from adult animals. Lymphoid cell numbers were varied from 1 x 10(6) to 8 x 10(6) cells/ml/culture and treated with a constant dose of THC or 11-OH THC. The smallest number of cells from the spleen or lymph nodes resulted in the greatest suppression. Thymus cells, however, were more readily suppressed than spleen or lymph node cells, regardless of the number of cells in culture. Furthermore, 11-OH THC suppressed the responses of the thymus cells to phytohemagglutinin more than to concanavalin A. The proliferative responses of spleen and lymph node cells from weanling mice to concanavalin A and phytohemagglutinin were much more readily suppressed than were cells from adult mice. This age-related difference was seen in the dose-response studies as well as in the studies with varying cell numbers in culture. In all cases, spleen and lymph node cells from younger mice were more readily suppressed to concanavalin A and phytohemagglutinin than those from older mice when treated with the cannabinoid preparations.