CXCL8 and bacterial infectious disease: The expression patterns of the pro-inflammatory cytokines tumor necrosis factor alpha (TNFα), interleukin 1 beta (IL-1β), interleukin 8 (IL-8), interleukin 6 (IL-6) and CD14 antigen (CD14), a pivotal cell surface protein mediating detection of bacterial cell wall components, were measured as representatives of early response innate immune genes that are typically up-regulated by bacterial infections of mammary tissue [12,14,27].