[Immunologic study of pleural neoplastic effusions: Detection of immune complexes and complement activation]

Occurrence of immune complexes in malignant pleural effusions has been investigated by the 125I-c1q binding test. 55% of the pleural effusions had C1q binding activity levels higher than those found in transudates used as controls. The levels of C1q binding activity in effusions were significantly higher than those found in the serum of the same cancer patients. High levels of C1q binding activity were found in malignant effusion independently of type or differentiation of the tumors involved. The C1q binding material had properties of immune complexes. The levels of CH50 and C3d, i.e. the degradation product of C3, in malignant effusion were similar to those of transudates. These observations show a high incidence of immune complexes in malignant effusions and a slight activation of complement inadequate for its local consumption. The persistence in major quantity of immune complexes in malignant effusion suggests local formation or decreased clearance.