CLQ ENHANCEMENT OF IGG-DEPENDENT EOSINOPHIL-MEDIATED KILLING OF SCHISTOSOMULA INVITRO

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  • 15 February 1987
    • journal article
    • research article
    • Vol. 138  (4) , 1240-1245
Abstract
Antibody-dependent eosinophil-mediated cytotoxicity plays a role in host protection against metazoan parasite invasion. We examined a possible role for C1q in eosinophil-mediated cytotoxicity by using a Schistosoma mansoni schistosomula killing system in vitro. The addition of monomeric purified human C1q enhanced IgG-dependent human eosinophil-mediated killing from 1.4-fold to 2.3-fold (mean percent killing 12% .+-. 4 vs 21% .+-. 4, p < 0.005) when the immune IgG concentration was low. In contrast, there was no significant enhancement of neutrophil-mediated killing. When the IgG concentration was increased fourfold, C1q did not cause enhancement of eosinophil-mediated killing (35% .+-. 9 vs 37% .+-. 5). Preincubation of eosinophils with type 1 collagen abrogated C1q enhancement of killing, raising the possibility of a receptor-mediated process, which depends upon cellular binding of C1q via the collagenous portion of the molecule. Eosinophils and neutrophils were examined for the presence of C1q receptors by using 125I labeled C1q. C1q binding to both cell types was saturable, reversible, and specific, indicating that binding is through specific receptors. Type I collagen inhibited binding of C1q to cell, suggesting that C1q binding is via the collagenous stalk of C1q. The number of receptors was approximately twice as high for eosinophils as compared with neutrophils (1.9 .times. 107 vs 1.1 x 107, p < 0.025). Affinity constants for the two cell types were similar (1.5 .times. 107 vs 1.3 .times. 107). These suggest that C1q and receptors for C1q on eosinophils may be important for eosinophil-mediated schistosomula killing.