CD4 and viral infectious disease: A reduction of lung and airway cellularity can reduce the amount of weight loss during viral infection, but despite a partial reduction in CD4+ T cells (Fig. 5g), F4/80+CD11b+ macrophages (Fig. 5h) and CD11c−SiglecF+ cells (Fig. 5i), no differences were observed in any other cell type analysed (Fig. 4).