Objective: To test the hypothesis that immunosuppression increases the development and progression of endometriosis in baboons.
Design: Experimental controlled study.
Setting: Institute of Primate Research, Nairobi, Kenya.
Participants: Thirty-two baboons (8 with normal pelvis, 10 with spontaneous endometriosis, and 14 with endometriosis induced by intraperitoneal seeding of menstrual endometrium).
Intervention: Daily injection of 0.8 mg/kg IM methylprednisolone and 2 mg/kg azathioprine for 3 months in 16 baboons (4 with normal pelvis, 5 with spontaneous endometriosis, and 7 with induced endometriosis). No treatment was given to the remaining 16 primates.
Main outcome measures: The change in number and surface area (mm2) of endometriotic lesions was evaluated by laparoscopy in all baboons after 3 months, in 8 animals with induced endometriosis and in 9 primates with spontaneous disease after 7 and 12 months, respectively.
Results: Immunosuppressed baboons with spontaneous endometriosis had a significantly higher number and larger surface area of endometriotic lesions than nontreated animals. However, immunosuppressed and nontreated primates with induced endometriosis were comparable with respect to both number and surface area of implants. A transient decrease in typical lesions was noted during immunosuppression. Immunosuppression did not cause the development of endometriosis in baboons with previously documented normal pelvis.
Conclusion: Immunosuppression may increase the progression of endometriosis in baboons with spontaneous disease.