Flow Cytometry-Based Assays to Quantify Complement Deposition and Neutrophil Uptake of Group A Streptococcus

Quantification of complement deposition and subsequent neutrophil-mediated uptake provides an important way to assess the role of different bacterial factors in evasion of the host innate immune response. Here, we describe flow cytometry-based methods to allow quantification of deposition of the complement opsonin C3 on the bacterial surface and subsequent uptake by primary human neutrophils. The assays outlined below provide key methods to determine whether specific bacterial factors are involved in the evasion of complement-mediated immunity, using widely accessible reagents and equipment.