Studies on the relationship between the estrous cycle of BALB/c mice and their resistance to Paracoccidioides brasiliensis infection.

A relationship between the estrous cycle and non-specific host resistance to Paracoccidiodes brasiliensis yeast cells was examined by using both sexes of adult BALB/c mice. They were divided into 6 groups, including a male group and females at proestrus, estrus, metestrus-I, metestrus-II and diestrus. The mice received yeast cells through three different inoculation routes; intravenous, intraperitoneal and intratracheal. In all of the inoculation routes, the clearance of the yeast cells was influenced by the estrous cycle. The female mice at estrus, which might have high blood estrogen levels, showed a marked clearance of the yeast cells from the blood, peritoneal cavity and lungs. These results suggested that non-specific host resistance to the yeast cells was enhanced by estrogen. All female groups inoculated by the three routes showed higher clearance of the yeast cells than the male group.