Fig. 1

Multivariate statistical analysis of samples in positive and negative ion modes. Principal components analysis (PCA) in negative (a) and positive (b) ion modes; orthogonal partial least-squares discriminant analysis (OPLS-DA) score chart in negative (c, e, g) and positive (d, f, g) ion modes. Figure c, e, and g: control cells incubated for 6 h, 12 h, and 24 h, respectively; d, f, and h: cells stimulated with IFN-γ for 6 h, 12 h, and 24 h, respectively. (-), negative ion mode. ( +), positive ion mode. QC, quality control