Figure 4. FH is important for P. pneumotropica survival in the presence of human serum.

Suspensions of P. pneumotropica (1×10³ cells) were incubated with human purified Factor H (FH) (125, 375 or 500 µg/ml) for 5 min at 37°C and 40% of FH-depleted human serum was added and incubated for 30 min at 37°C. Suspensions were then centrifuged and the bacterial pellet was suspended in PBS and 100×diluted before spreading on LB plates. A negative control was included containing no purified FH before treating P. pneumotropica with FH-depleted serum. The percentage of survival was calculated considering 100% as the number of colonies obtained after P. pneumotropica treated previously with 500 µg/ml FH before adding FH-depleted serum. Data were analyzed using ANOVA; *p<0.05.