The role of myeloid cells in prevention and control of group A streptococcal infections

Group AStreptococcus (GAS;Streptococcus pyogenes) is one of the most versatile bacteria among human pathogens. Non-invasive GAS infections can cause common diseases, such as pharyngitis and impetigo. Severe invasive GAS infections can lead to rapid progressive and life-threatening manifestations, including necrotizing fasciitis and streptococcal toxic shock syndrome with high mortality rates ranging from 30% to 70%. Therefore, GAS is also known as "killer microbes" or "flesh-eating bacteria" . During severe invasive GAS infections, anti-bacterial immunity is impeded by attenuation of the cellular components of innate immune responses. However, this loss of protection is compensated for by interferon-γ-producing immature myeloid cells, which are recruited upon severe invasive GAS infections in mouse models. In this review, we discuss and summarize the current knowledge on the role of interferon-γ-producing myeloid cells and other myeloid cells in the prevention and control of severe invasive GAS infections.