Table 4.

Effect of tuberculosis and diabetes on innate immune cell function

Cell type	Function during infection	Effect of tuberculosis	Effect of diabetes	References
Neutrophils	Phagocytosis	↑ Neutrophils	↑ Neutrophils	27,41,59,65,67,74
	Bactericidal activity	↑ TNF-α, IL-8, IL-17,	↑ TNF-α, IL-6, IL-8, IL-17,
	Acute inflammatory response	CXCL9, ROS, defensins	CCL2, ROS #x2193; NOx, CXCR2, chemotaxis
	Removal of microbes and dead tissue
	Promote M1 polarization
Type 1 (M1) macrophages	Classically activated,	↑ M1	↑ M1	86–90,94
	proinflammatory responses	↑ TNF- α, IL-1β, IL-6,	↑ TNF-α, IL-1, IL-1β, IL-6, IL-8,
	Bacterial, protozoa and	IL-18, IL-12, IL-23, CCL2,	IL-12, IL-23, CCL2, ROS, MMP-9
	viral defence	NOx, ROS	↓ NOx
	Antigen presentation and T cell activation
Type 2 (M2) macrophages	Alternatively activated,	↑↓ M2	↓ M2	150–154
	anti-inflammatory responses	↑ TGF-β, MMP-12	↑↓ IL-10
	Antagonise M1 responses	↑↓ IL-10
	Wound healing/fibrosis
Natural killer (NK) cells	Defence against intracellular	↑ NK	↑↓ NK	25,100,101,104,105,155
	pathogens	↑ IFN-γ, TNF-α, IL-22,	↑ TNF-α, IL-8, IL-22, CCL2	105,155
	Contain intracellular	ICAM-1, Th1 response	↑/– IFN-γ
	infections prior to adaptive response
	Release cytotoxic granules
	Induce apoptosis of infected cells
	Antibody dependent cellular cytotoxicity
Natural killer T (NKT) cells	Shared properties of NK and	↑ NKT	↑↓ NKT	104,106–110
	T cells for regulation of	↑ IFN-γ, TNF-α, GM-CSF,	↑↓ IL-4, IL-10
	immunity	DC maturation, CTL response	↓ IL-4
	Respond to lipid antigens	↑ IFN-γ, TNF-α; ↑↓ IL-10
	Cytokines promote either
	inflammation or tolerance
	May have cytotoxic functions
Dendritic cells (DC)	Antigen presentation	↑ DC	↑↓ DC	88,111–113,156
	Phagocytic when immature	↑ DC migration	↑ TNF-α, IL-1β, IL-6, IL-12,
	Antigen uptake and presentation	↑ Antigen presentation	IL-23, GM-CSF
	T cell activation	↑ TNF-α, IL-1β, IL-6, IL-12,
	Initiate adaptive immune response	IL-18, IL-23, IL-27, TGF-β
	Link between innate and adaptive immunity

↑, increased; ↓, reduced; ↑↓, increased or reduced (conflicting evidence); –, no change; CCL2, chemokine CC motif ligand 2; CTL, cytotoxic T cells; CXCL9, chemokine C-X-C motif ligand 9; CXCR2, chemokine C-X-C motif receptor 2; GM-CSF, granulocyte macrophage colony-stimulating factor; ICAM-1, intercellular adhesion molecule 1; IL-1β, interleukin-1β; IL-4, interleukin-4; IL-6, interleukin-6; IL-8, interleukin-8; IL-10, interleukin-10; IL-12, interleukin-12; IL-18, interleukin-18; IL-22, interleukin-22; IL-23, interleukin-23; IL-27, interleukin-27; IFN-γ, interferon-γ; MMP-9, matrix metalloproteinase-9; NOx, mono-nitrogen oxides; TGF-β, transforming growth factor-β; TNF-α, tumour necrosis factor-α; ROS, reactive oxygen species.