Comparison of the kinetics of cytokine pattern in RSV challenged chickens of different congenic lines. Classification of individual responses by PCA and discriminant analysis in immunized and non-immunized groups of regressors (A) and progressors (B). Samples were classified into three groups by using PCA (XLSTAT software). The first group (blue spots) includes samples taken on the time of challenge, the second group (green spots) includes samples obtained 14 days after challenge and the third group (brown spots) comprises samples obtained 28 days after challenge. F1 and F2 represent the two main components.