The study of the plasma cells in the hamster vagina reveals that a cyclical variation of these cells, parallel to the level of oestrogen in the animal, exists in the mucosa under normal and experimental conditions. At oestrus, the lamina propria shows a small number of plasma cells. At di-oestrus, the plasma cells increase in number and accumulate beneath the epithelium. A few plasma cells are found between the epithelial cells. The concentration of plasma cells and their migration is greater still after castration. Administration of oestrogen to castrated animals provokes a remarkable decrease in the number of plasma cells situated in the lamina propria and their disappearance from the epithelium.
These findings demonstrate that a cyclical variation of plasma cells in the hamster vagina exists which can be regulated by oestrogens. We suggest that these phenomena are related both under normal and experimental conditions to an immunological response situated in the vaginal mucosa.