Cyclosporine reduces the spleen dimensions in rabbits.

PURPOSE: To assess the influence of prolonged cyclosporine use on the macro- and microscopic morphology of the spleen. METHODS: 16 adult rabbits were divided into two groups (n = 8): group 1 - a placebo group, which was followed-up over a period of nine months; group 2 - which had taken an oral dose of cyclosporine (10 mg·kg-1·day-1) over nine months. At the end of this period, the splenic histoarchitecture of all animals was evaluated and the splenic corpuscles were measured. RESULTS: The spleens of the first group presented normal characteristics and dimensions. The second group, however, had a reduction in all dimensions and its tissue texture had become soft. The white pulp and the perivascular sheath had become reduced in size and the number of lymphoid follicles had also fallen (p = 0.002), manifesting less splenic corpuscles (p = 0.0012) and lymphocyte nuclear pigments (p = 0.03). CONCLUSIONS: Prolonged use of cyclosporine reduces the spleen size, transforming it into a soft organ associated with a decrease in white pulp, perivascular sheath, lymphoid follicles and nuclear pigments in rabbits.