αil 21r

Influenza-infected WT mice were administrated with control IgG or various neutralizing or depleting Ab as described in the related Results sections. For CD4⁺ T cell depletion with high dose of α-CD4, mice were injected with 250 μg of α-CD4 weekly (clone: GK1.5, BioXCell) starting at 14 d.p.i. For circulating CD4⁺ T cell depletion, mice were intraperitoneally injected with 40 μg of α-CD4 for the first dose followed with 10 μg of α-CD4 weekly. CD40L blockade was achieved by the injection of 250 μg of α-CD40L (clone: MR-1, BioXCell) weekly, respectively. For systemic IL-21R blockade, 500 μg of α-IL21R (clone: 4A9, BioXCell) was injected intraperitoneally weekly starting at 14 d.p.i. For lung local IL-21R blockade, 50 μg of α-IL21R was injected through intranasal route weekly starting at 14 d.p.i. In some experiments, FTY720 (1 mg/kg; Cayman) was administrated via intraperitoneal injection daily from 13 d.p.i. to block lymphocyte migration until mouse euthanasia.