CD8A and influenza: Proinflammatory cytokine concentrations and viral loads were measured in lungs homogenates 2 and 4 d.p.c. The percentage of T-regulatory cells and the level of influenza-specific CD8+ T-cellular immune response were estimated in lungs 4 d.p.c. The relative content of innate immune cell populations was analyzed right before heterologous infection (0 d.p.c.)and on 1 and 4 d.p.c.