PRF1 and pneumococcal infection: In human clinical specimens, concentrations of cytolysins can be very high ranging from 0.33 μg/mL to 399 μg/mL (Badiou et al., 2010), and, in pneumococcal infections, these can rapidly increase through the release of PLY as result of pneumococcal autolysis (Jacques et al., 2020; Mellroth et al., 2012).