Table 1. The diversity of TNTs.

Cell type	Length	Thickness	Cytoskeleton	Membrane detection	Refs
PC12	Avg. 6 μm*	50 - 200 nm	actin, no microtubules	WGA-staining, SEM	1
HEK293	N/A	< 500 nm	actin, no microtubules	GFP-PrPwt-transfection	41
Jurkat T cells	Avg. 22 μm, max 100 μm	< 380 nm	actin, no microtubules	DiD-staining, TEM	7
ARPE-19	Avg. 44 μm, max 120 μm	50 – 300 nm	actin, no microtubules	DIC, WGA-staining, SEM	11
NRK	Max 70 μm	N/A	actin, no microtubules	DIC, WGA-staining, SEM	2,12
HeLa	Avg. 17.7 μm, max 40 μm	N/A	actin, no microtubules	WGA-staining	35
Cardiac myoblast H9c2 cell	Max 100 μm	< 1000 nm (AFM)	actin and microtubules	DIC, DiD-staining	42
Human lung carcinoma A549	Max 105 μm	400 – 1500 nm	actin and microtubules	Brightfield	43
Human monocyte-derived macrophages	N/A	700 nm	actin, microtubules **	Brightfield	3
Primary neurons and astrocytes	Avg. 7.1 μm	N/A	microtubules, actin ***	DIC	9

WGA, wheat germ agglutinin; DiD, Vybrant^® DiD celllabeling solution; SEM, scanning electron microscopy; TEM, transmission electron microscopy; DIC, differential interference contrast; AFM, atomic force microscopy. * Unpublished data; ** All nanotubes contained actin, and a subgroup also contained microtubules; *** All nanotubes contained microtubules, and a subgroup also contained actin (65%).