COMPLEMENT ACTIVATION ON SOLID-SURFACES AS DETERMINED BY C3 DEPOSITION AND HEMOLYTIC CONSUMPTION

Complement activation was investigated on hydrophilic and hydrophobic glass beads incubated in serum. Very little complement activation was detected with these surfaces, as indicated by a hemolytic assay and by measurement of the amount of iC3b appearing in the solution. However, preadsorption with IgG at the hydrophobic and hydrophilic beads resul ted in complement activation on both surfaces. We also investigated de pendent deposition of C3 at hydrophobic and hydrophilic silicon surfac es when the complement was activated. The chemistry of those surfaces is similar to the hydrophobic and hydrophilic beads. Ellipsometry, an optical method, was used for determination of the amounts of organic m aterial deposited at the surface. C3 deposition was observed at the Ig G precoated hydrophobic surface but not at the IgG-coated hydrophilic surface. The absence of C3 deposition at the hydrophilic surface was p robably due to reversible binding of IgG. However, precoating of the h ydrophilic surface with a double layer of IgG and anti-IgG resulted in C3 deposition also at the hydrophilic surface. The results illustrate that methods based on measuring deposition of C3 at surfaces, such as immunofluorescence or ellipsometry, cannot exclude surface-associated complement activation that is probably due to reversible binding of t he complement components of the activated molecule. On the other hand, it has previously been shown that determination of complement activat ion in solution with the use of a C3a assay cannot exclude surface-ass ociated activation due to immobilization of C3a at the surface.(1) Thi s methodologic question is an important issue because factors such as C3a and C5a act as soluble anaphylatoxins, whereas deposited factors s uch as C3 act as cellular receptors. (C) 1994 John Wiley and Sons, Inc .