FCAR and Respiratory tract infection: In order to understand the effect of polyclonal Ig formulations, specifically the prototypic mIgA and IgG formulations, in controlling respiratory tract infection and to determine the role of CD89 in this, we infected CD89tg/wt/LyzMcre/wt and LM mice with a lethal dose of PR8 virus, and survival and body weight were observed over the course of 14 days.