The present study was conducted to investigate the effect of kefir, koumiss, milk and yoghurt administration on plasma cells, which synthesize specific antibodies against antigens, and mast cells, which have a role in the regulation of humoral and cellular events, in the mice spleen tissues. Mice (n=30) were divided into 5 groups. As a result of statistical evaluation, live weights of mice in kefir, koumiss, milk and yoghurt groups were found to be increased compared to the control group. When numbers of plasma cells in spleens of mice treated with kefir, koumiss, milk and yoghurt were checked with stereological methods, significant difference was found to be increased in number of plasma cells of kefir-treated mice compared to other groups at the end of 15 days. At the end of day 15, a significant difference was found to be increased in the number of mast cells in the spleen of milk-treated mice compared to control group. As the number of plasma cells in the spleen is at higher level with kefir, than with koumiss, milk and yoghurt; also there being a significant difference between the numbers of mast cells in the spleens of mice treated with milk compared to control group, this is remarkable for healthy eating/functional food.