Fig. 4.

C3-deposition and Sia-siglec recognition. (a) Increased Sia on PA leads to decreased C3-deposition. Sia-positive bacteria∗ (%SNA⁺ cells) and acquired Sia was quantitated ∗∗ fluorimetrically. The CFU of neuraminidase, ∗∗∗ untreated and ∗∗∗∗ treated PA was detected by bactericidal assay. (b) FITC-PA binds with CHO-siglec-7,-9. Binding of untreated (PASia⁺) or neuraminidase-treated (PASia⁻), (bold-line) is compared with only CHO-cells (thin-line). Binding of PASia⁺ with (a) CHO-siglecs compared to PASia⁻; (b) preincubated CHO-siglecs with the respective anti-siglec-7,-9 antibodies; (c) unmasked CHO-siglecs by sialidase; and (d) preincubated sialidase-treated CHO-siglecs with the respective anti-siglecs antibodies.