The number and distribution of immune cells in the cervicovaginal mucosa remain constant throughout the menstrual cycle of rhesus macaques.

A number of studies have shown that the ovarian hormone cycle affects genital tract immunoglobulin (Ig) levels and T cell function in both humans and rhesus monkeys. We hypothesized that shifts in immune cell populations occurring in response to hormone cycles are involved in the observed changes in genital tract immunity. To test this hypothesis, we characterized the type, number, and distribution of immune cells in the cervicovaginal mucosa at different stages of the menstrual cycle. Tissues from 18 normal female rhesus macaques were studied by immunohistochemistry and computerized morphometric analysis. The number and distribution of CD1a+ Langerhans' cells, CD2+, CD3+, CD4+, and CD8+ T cells, CD20+ B cells, and surface Ig+ plasma cells did not change in samples collected at the different stages of the cycle. However, in no relation to the stage of the menstrual cycle, the number of Langerhans' cells and other immune cell types was different in the various regions of the cervicovaginal mucosa examined. In addition, variation in thickness of the ectocervical and vaginal epithelium during a normal menstrual cycle of rhesus macaques is not accompanied by changes in intraepithelial immune cell populations. We conclude that steroid hormones do not influence genital mucosal immunity by changing the number or distribution of immune cells in the lower reproductive tract.