Sex hormones modulate the response of pulmonary perivascular inflammation to cyclophosphamide therapy in MRL/MpJ-lpr/lpr mice.

Responses of pulmonary perivascular infiltrates to immunosuppressive therapy with cyclophosphamide (CY) were evaluated in the MRL/MpJ-lpr/lpr (MRL/1) mouse, a model for the study of systemic lupus erythematosus. Male and female mice were divided into the following groups: controls injected with saline; intact mice receiving CY; castrated CY-treated mice; castrated, hormone implanted, CY-treated mice. CY treatment began at 30 days of age and animals were killed at 60 days of age. Lungs were fixed-inflated to 26 cm H2O pressure with glutaraldehyde-formaldehyde fixative. The pulmonary perivascular response to immunosuppressive therapy was graded depending on the extent of infiltrates surrounding 15 pulmonary vessels per animal. Intact males treated with CY alone had almost complete clearing of perivascular infiltrates, whereas intact females did not respond to therapy. Castrated CY-treated males showed a decreased response to CY compared to intact CY-treated males. Castrated, estradiol-implanted males had no response to CY therapy. Estradiol interfered with the therapeutic response to CY in male MRL/1 mice.