Principal component analysis of pulmonary expression of the 10 host-encoded mRNAs in mock-treated and infected DBA/2J and C57BL/6J mice in the 5-day time course of IAV infection. mRNA levels of Fos, Retnla, Irg1, Il6, Il1b, Cxcl10, Stat1, Ifng, Ifnl2, and Mx1 were determined by qRT-PCR as outlined in the Methods section, using Actb and Rpl4 mRNA expression for internal normalization. Each dot refers to the mean value of mice of one treatment as outlined in the legend adjacent to the box. The number inside each dot identifies the time (h) elapsed since t = 0 h. A. Results obtained with the DBA/2J strain. B. Results obtained with the C57BL/6J strain. Including the third component did not lead to further discrimination (data not shown).