Effect of testosterone on the eosinophil response of C57BL/6 mice to infection with Brugia pahangi.

The kinetics of peripheral and bone marrow eosinophil responses of C57BL/6 mice against Brugia pahangi infection were compared between both sexes, and the effects of testosterone on these eosinophil responses were examined. At the early phase of infection (7 to 10 days), female mice showed significantly higher peripheral eosinophil response than did males, and on day 5, 7 and 10 postinfection bone marrow eosinophil responses were also high in females. Live infective larvae but not dead ones could induce these differential responses of eosinophils between sexes. Castration of male mice increased the peripheral and bone marrow eosinophil responses to the levels of female mice, whereas castration of female mice did not affect these responses. Furthermore, testosterone treatment at a pharmacological dose in female mice suppressed peripheral and bone marrow eosinophil responses at the early phase of infection. These results suggest that the male sex hormone, testosterone, but not the female sex hormone has a role in the down-regulation of the systemic eosinophil responses of C57BL/6 mice to infection with B. pahangi.