Effect of d-fenfluramine on the local immune response to the opportunistic microbial pathogen Candida albicans

In this study the effects of systemic administration of d-fenfluramine on the local lymphocyte response to Candida albicans was evaluated. Experimental animals were challenged intradermally with Candida albicans and then administered d-fenfluramine (d-FEN 1 mg/kg per day, i.p.) or a balanced salts solution. At successive time intervals, lymphocytes were derived from the draining lymph nodes and from the dermal sites of active microbial challenge. A CD8+ lymphocytosis was observed in all animals challenged with Candida albicans. The CD8+ lymphocytosis was augmented in animals that received d-FEN. Phenotypically, lymph nodes from d-FEN treated animals showed a marked increase in CD3+ and CD8+ lymphocytes, a modest increase in the numbers of NK1.1+ cells and a decrease in Ig+ lymphocytes. Functionally, lymphocytes from the site of active microbial challenge were capable of direct growth inhibition of Candida albicans. The anti-fungal activity was augmented in the animals that received d-FEN. These results suggest that d-FEN augments the local T lymphocyte response to an important microbial pathogen by increasing the number of T lymphocytes draining the site of microbial infection and by increasing the biological activity of the lymphocytes at the site of the infection.