F(ab')2 segment is the active component of immunoglobulin G autoantibody generation in patients with endometriosis.

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.

INTERVENTIONS

None.

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.