CCL4 and infection: These receptors mediate the onset of infection recognition by macrophages and mast cells, leading to chemokines such as macrophage inflammatory factors (MIP‐1a and MIP‐1β), interleukin‐8 (IL‐8), inflammatory cytokines such as interleukin‐1β (IL‐1β), tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), and vasoactive amines, among many other inflammatory mediators, which will give rise to localized inflammatory exudates: Neutrophils confined to blood vessels pass through the small postcapillary veins into the extravascular tissue at the site of infection (or injury).