FOXO3 and Salmonella Infections: Based on the above analysis, it is hypothesized that the hyperactive FoxO3 in susceptible chickens might both enhance apoptosis of T, and B lymphocytes and macrophages in the spleen, and constrain production of Th1 and Th2 cytokine, all of which are necessary for immunological clearance during the early stage of Salmonella infection.