CD4 and infection: Liman and Rautenschlein [7] demonstrated a significant increase in the percentage of CD4+ T lymphocytes with concurrent upregulation of IL-6 and/or IFN-γ in the Harderian gland (HG) after vaccination or infection with aMPV/A or B. Conversely, Cha [17] reported an increase in the percentage of CD8+ T cells, but not in CD4+ T cells, in the upper respiratory tract after aMPV/C inoculation.