Raman Microspectroscopy of monocytes infected with C. pneumoniae . A) Score plot based on Principal Component Analysis (PCA). Monocytes infected with C. pneumoniae for 48 h (red dots) were separated from uninfected cells (blue dots), whereas no difference was observed after 6 h of infection (orange dots) compared to control. B) Mean spectra plot of PC-1 indicating the wavenumber regions which were mainly responsible for the differences between uninfected and infected monocytes after 48 h. Peaks shown in dark grey correspond to the wave number regions which are mainly responsible for data separation. The percentage of data defining the separation is indicated.