Studies on murine models of S. pneumoniae pneumonia using immunocompetent mice described that the respiratory pathogen increases the production of inflammatory mediators such as TNF-α, IL-1, IL-6, LTB4, NO, KC (CXCL1), MIP-2 (CXCL2), MCP-1 (CCL2) and RANTES (CCL5) and induces neutrophils and macrophages infiltration in the lung [17], [18]. This evidence concerns the gene CXCL2 and susceptibility to pneumonia measurement.