Fig. 7. SpC3 binds to yeast surfaces. Coelomic fluid was obtained from sea urchins that had received two injections of LPS at 2-day intervals and was collected 2 days after the second injection. Yeast were incubated with ASW or CF, and SpC3 was detected on the yeast surface with anti-SpC3'pep (primary; 1°) and G RIgAP (secondary; 2°) followed by substrate incubation in 4-nitrophenol phosphate prior to absorbance readings at 415 nm. Yeast+ASW, yeast were incubated with ASW but antibodies were omitted prior to analysis; yeast+CF, yeast were opsonized with CF but antibodies were omitted prior to analysis; yeast+CF+2°, yeast were opsonized with CF but only the 2° antibody was used prior to analysis; yeast+CF+1°+2°, yeast were opsonized with CF and incubated with 1° and 2° antibodies prior to analysis; yeast+1°+2°, yeast were incubated with ASW and 1° and 2° antibodies were added prior to analysis. Values are means ± S.E.M.(N=3).