Age-related changes of the susceptibility to infection with Brugia pahangi in male and female BALB/c mice.

Effects of host age and sex on murine Brugia pahangi infection were examined. In female BALB/c mice, partial resistance to B. pahangi developed rapidly with age. In animals inoculated at 5-6 wk of age, resistance was about 2 times higher than in the youngest group (2-3 wk) and remained at a similar level through the study period (12 wk). Male BALB/c mice showed a similar tendency until 5-6 wk of age, but afterward their susceptibility increased with age. Significant difference in the susceptibility was detected between sexes after sexual maturation. After macrophage blockade by an injection of carbon particles into the mice, the age- and sex-related differences were completely abolished. This suggests that macrophages might have an important role(s) in the age- and sex-related changes of susceptibility to B. pahangi in BALB/c mice.