Fig. 4. Opsonic activities of coelomic fluid (CF; number of yeast phagocytosed per 100 coelomocytes) plotted against the SpC3 concentration of CF (relative intensities) collected from the same sea urchin. Sea urchins (N=18) were injected with either LPS or ASW on day 0 and day 4. Coelomic fluid was collected on day –1, day 1 or day 5. SpC3 titers were determined by densitometric analysis of western blots on which SpC3 was stained with anti-SpC3-6H. Values are means ± S.E.M.(N=3).