Fig. 3

Characterization of FTV. A The particle size distribution histogram measured by NTA. B Western blot of Tetraspanin 4, integrin α5, LAMP1, CD63 and CD68 in FTV and cell lysate of macrophage. n = 5. C SEM images of FTV on different formation stages. In the initial stage, FTV originated from the primary filopodia. During the middle stage, the size of FTV increases while they maintain their connection to the filopodia. Following that, some FTV displayed surface cracks. Finally, FTV were released from the filopodia and scattered in the vicinity. Scale bar: 500 nm. D Immunofluorescence staining of Tetraspanin 4 (green) and Integrin α5 (green) in FTV. 40x objective. E Immunogold labeling of Tetraspanin 4 was detected in the plasmalemma of FTV (above) and in nanotubular filopodia (below). Scale bar: 250 nm. F Tetraspanin 4-GFP marked FTV (arrows). 40x objective