Bench-to-bedside review: Bacterial pneumonia with influenza - pathogenesis and clinical implications

Table 1 Predisposing factors identified for combined viral/bacterial pneumonia and/or post-influenza pneumonia

	Factors associated with combined viral/bacterial infection	Factors associated with post-influenza pneumonia
Viral factors	Viral neuraminidase [37, 38]	Not involved, that is, virus is cleared [28, 29]
	PB1-F2 [39]
Bacterial factors	Pneumococcal surface protein A [40]	Unknown
Mechanical factors (host)	Epithelial injury [30]	Unknown
	Mucociliary velocity [33]
Immune cells (host)	Neutrophil function [34, 47, 49, 51, 57]	Neutrophil function [28]
	Neutrophil recruitment [52, 53, 55]	Neutrophil recruitment [29]
	Neutrophil apoptosis [48, 54]
	Macrophages [57, 58]
	Monocytes [57]
Cytokines/chemokines (host)	IFN-γ [59]	IL-10 [28]
	IFN-α/β [53]
	KC [53]
	MIP-2 [53]
Pattern recognition receptors (host)	MARCO [59]	TLR2 [29]
		TLR4 [29]
		TLR5 [29]
Metabolic enzymes (host)	Unknown	Indoleamine 2,3-dioxygenase [61]

Abbreviations: IFN, interferon; IL, interleukin; KC, keratinocyte-derived chemokine; MARCO, macrophage receptor with collagenous structure; MIP, macrophage inflammatory protein; TLR, Toll-like receptor

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