Validation of microarray data by ELISA. PCV2-induced changes in secreted levels of IFNγ (A), TNFα (B), IL-6 (C) and IL-8 (D). The protein levels in culture supernatants of mock-inoculated and PCV2-infected PAMs were measured by ELISA. Data are expressed as ng/L of three independent experiments. * 0.01 <p <0.05 and ** p<0.01 for PCV2-infected vs. mock-inoculated groups for the corresponding HPI.