COMPARISON OF COMPLEMENT ACTIVATION IN-VITRO BY DIFFERENT ECHINOCOCCUS-GRANULOSUS EXTRACTS

In the present study we have investigated and compared in vitro the sp ecific complement (C) activating activity of three metacestode prepara tions of Echinococcus granulosus. Extracts from hydatid cyst fluid (HC F-ext), protoscoleces (PSC-ext) and hydatid cyst membrane (HCM-ext) ac tivated human C producing C3 conversion and generating the C5b6 comple x and the terminal C complex (TCC). HCM-ext showed much lower C activa ting activity than PSC-ext and HCF-ext. Moreover, its ability to gene, ate C5b6 and TCC was lower than its ability to convert C3. On the oth er hand, PSC-ext and HCF-ext proved to be good C activators when their specific C activating activities were compared with that of inulin. H owever, PSC-ext produced lower levels of TCC than those produced by HC F-ext, in spite of the fact that both produced practically the same le vels of C3d and C5b6. These results may be consistent with the existen ce of several mechanisms of C modulation involved in the defence of th e parasite against host C damage.