ICAM1 and infection: Consequently, when ICAM-1/2-/- mice were pre-infected with non-lethal doses of X31 influenza and then subjected to a secondary infection with a high dose of the heterosubstypic PR8 strain 40 days later, the ICAM-1/2-/- mice were fully protected with comparable efficacy to that of WT mice from the heterosubtypic influenza infection (Figure 7E).