Objective: To determine if the low titer antiendometrial antibody detection by indirect immunofluorescence (IIF) in the sera of patients with endometriosis is because of specific antigen-antibody interactions.
Design: Sera of selected patients subjected to separation of immunoglobulin fragments by ammonium sulfate precipitation and pepsin digestion and tested by IIF. In a comparative method, a fragment, crystallizable (Fc) flooding technique was used to determine the active component.
Setting: Sera obtained preoperatively in the outpatient and results matched with surgical findings.
Patients/participants: Patients 45 years of age or less presenting for gynecological surgery who had signed an informed consent for the drawing of preoperative blood.
Main outcome measures: Indirect immunofluorescence was graded according to the intensity of staining and the lowest dilution at which staining occurred.
Results: All of the sera of the 11 patients with endometriosis exhibited F(ab')2 specific staining but none exhibited Fc fragment staining. None of the 7 control patients displayed F(ab')2 or Fc fragment staining.
Conclusions: F(ab')2 fragment is the active component of an immunologically specific interaction when antiendometrial antibodies are detected in the sera of patients with endometriosis.