CD86 and infection: To establish if infection with a low-pathogenic H5N1 virus results in higher activation of innate immune cells, we infected C57BL/6 mice with a recombinant H5N1-green fluorescent protein (GFP) (A/Vietnam/1203/2004) or H1N1-GFP (A/Puerto Rico/8/1934, PR8 strain) virus and measured the activation status of different cell populations in the lungs by quantifying cell surface upregulation of CD86.