C5 and infectious meningitis: Inhibition of the classical pathway and of C5 were both protective against meningitis caused by S. pneumoniae in rodents (Zwijnenburg et al., 2007; Woehrl et al., 2011), and a single nucleotide polymorphism of C5 (rs17611, encoding V802I) was associated with poor outcome in pneumococcal meningitis patients (Woehrl et al., 2011), indicating that the activation of the classical complement pathway plays a key role in the pathogenesis.