Fig. 1.

SSL7 inhibits generation of C5a during staphylococcal opsonisation. (A,B) Staphylococci were treated with 10% human serum for 30 minutes at 37°C in the presence of 0 – 450 nM SSL7 or SSL10. In one case (“SSL7 after”), 450 nM SSL7 was added to serum supernate after opsonisation. C5a generation was measured by using supernates as stimuli for calcium mobilization in U937-C5aR cells. Results depict in (A) representative calcium mobilization plots and in (B) mean values ± SEM of three independent experiments and are expressed relative to cells treated with supernate without staphylococcal proteins. In (A), “background” and “control” represent cells stimulated with untreated serum and serum after opsonisation without SSL7, respectively. (C) Cell-bound C5 convertases were constructed on staphylococci by initial deposition of C3b and subsequent addition of soluble fD, fB, and properdin. C5 was subsequently added in the presence of 0 – 450 nM SSL7, and C5a generation in the absence of IgA was analysed by using supernates as stimuli for calcium mobilization in U937-C5aR cells. Results represent mean values ± SEM of three independent experiments and are expressed relative to cells treated with supernate without SSL7.