In the absence of infection, the splenic phagocyte population (CD4− CD8a− CD19− B220− CD11b+ splenocytes) of VAD mice contained a significantly (P < 0.05) larger proportion of neutrophils (CD4− CD8a− CD19− B220− CD11b+ Ly6G+ splenocytes) compared with control mice (Fig. 1e,f and Extended Data Fig. 1f). This evidence concerns the gene CD4 and infection.