Peripheral blood leukocyte subsets following infection of naïve animals with Perth/16 and NY/21.

Ferrets were bled on days 0–7, 9, 11, and 13 relative to the day of viral challenge, and cells were stained and analyzed by flow cytometry as described in the text. (A) Total white blood cell counts were obtained using a Hemavet apparatus. Percentages of (B) CD3-positive cells (T cells), (C) CD8-positive cells (cytotoxic T lymphocytes), (D) TH cells (CD3+ and CD4+), (E) CD79a-positive cells (B cells), and (F) CD11b-positive cells excluding CD11b-high/FSC-high cells (granulocytes) were measured. For each animal the frequencies were normalized to the ferret’s values on day 0; the Y axis represents percent of values on day 0. “Mock”, unvaccinated mock-infected animals; “H3N2”, unvaccinated animals challenged with Perth/16; “H1N1pdm”, unvaccinated animals challenged with NY/21. † indicates p<0.0001; * indicates 0.0001