Figure 1. Preparation and properties of anti-streptococcal IgG (E-IVIG).

(a) IVIG promotes neutrophil uptake of S. pyogenes. FITC labelled S. pyogenes cells were treated with 5 mg/ml of IVIG (black bars) or PBS (grey bars) and incubated with freshly isolated human neutrophils. Results from three independent experiments are expressed as percentage of FITC⁺ neutrophils (mean ± SD) after a 30 min co-incubation. n = 3, two-tailed t-test: p = 0.0003 (H364, H366 and H599); p = 0.0002; (H471); p = 0.0021 (H530); p < 0.0001 (H293); p = 0.0069 (H395). (b) Concentration-dependent binding of M1 S. pyogenes cell wall extract by E-IVIG (white triangles) and IVIG (black squares). (c) Serotype-independent binding of S. pyogenes cell wall extracts by E-IVIG (white bars) IVIG (black bars), at a fixed concentration (2500 ng/ml). Results from three independent experiments are expressed as triplicate A₄₅₀ readings minus the background absorbance (mean ± SD). n = 3, two-tailed t-test, p < 0.0001 in all instances.