Besides chemokines, cytokines such as TNF-α are released acutely in response to injury or infection [44, 45], and function to initiate and maintain the inflammatory process in part by stimulating other pro-inflammatory cytokines (e.g., IL-1α, IL-1β, and IL-6 [65, 66]) and chemokines (e.g., CCL2, CCL3, and CXCL2 [67, 68]). Here, CCL2 is linked to infection.