IFNG and coinfection: Regarding cytokine secretions, co-infection of B. cereus and H9N2 induced lower IL-2 and IFN-γ while IL-6 levels were upregulated in contrary to those of the control group, indicating imbalance in the immune response of Th1/Th2 and the reduced IL-2 in the groups initially infected with B. cereus might facilitate AIV H9N2 to survive and more severe lesions in the lungs due to Th1/Th2 imbalance.