Fig. 2. Opsonic activities of different concentrations of coelomic fluid (CF). Sea urchins received two injections of LPS at 2-day intervals and CF was collected 3 days after the second LPS injection and diluted with ASW (% CF) before being used to opsonize yeast for 40 min. Phagocytosis was allowed to proceed for 45 min. PSI, phagocytic stimulation index (see Materials and methods). Values are means ± S.E.M.(N=8).