Complement components and their activation products in pleural fluid.
OBJECTIVE
The aim of this study was to determine the role of complement components in pleural effusion measured with novel markers of complement activation, to assess which pathway of activation is predominant in different diseases, and to find out whether the analysis of complement components and their activation products could help in diagnostic procedure differentiating the etiologies of pleural effusion.


METHODS
The study population consisted of 71 patients who had pleural effusion secondary to tuberculosis (n=23), rheumatic disease (n=10), or malignancy (n=38).


METHODS
Complement components and their activation products, including the soluble terminal complex SC5b-9, were measured in plasma and pleural fluid.


RESULTS
In all patients with rheumatic pleurisy, pleural fluid SC5b-9 was higher than 2 AU/mL and in all patients with malignant pleural fluid it was lower than 2 AU/mL. The mean level of SC5b-9 in rheumatic pleural effusion was also significantly higher than in tuberculosis. In addition, the concentrations of pleural fluid C3 and C4 were significantly lower and the ratio C4d/C4 was significantly higher in rheumatic compared with tuberculous or malignant pleurisy. In plasma, both SC5b-9 and C1s-C1r-C1INH-complexes were significantly higher in rheumatic subjects than in other patients. In stepwise multinominal logistic regression analyses, the most significant predictors for rheumatic pleural fluid were high pleural fluid SC5b-9 and low C4.


CONCLUSIONS
These observations indicate that the complement cascade is activated through both the classic and the alternative pathways in rheumatic pleurisy. Determinations of SC5b-9 and C4d/C4 in pleural fluid were the best variables differentiating rheumatic, tuberculous, and malignant effusions.
Salomaa
E R
ER
Department of Pulmonary Diseases and Clinical Allergology, Turku University Hospital, Finland. eirisa@utu.fi
Viander
M
M
Saaresranta
T
T
Terho
E O
EO
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000150:complications; D003167:Complement Activation; D003172:Complement C1 / Q000032:analysis; D003176:Complement C3 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis; D011415:Complement Factor B / Q000032:analysis; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins / Q000032:analysis*; D005260:Female; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000097:blood / Q000209:etiology / Q000276:immunology*; D016066:Pleural Effusion, Malignant / Q000097:blood / Q000276:immunology; D014396:Tuberculosis, Pleural / Q000150:complications
D003172:Complement C1; D003176:Complement C3; D003181:Complement C4; D015938:Complement Membrane Attack Complex; D006023:Glycoproteins; C047610:SC5b-9 protein complex; D003165:Complement System Proteins; D011415:Complement Factor B