Electron microscopic in vivo appearance of s.c.-injected NPCs in draining lymph nodes.
A, Transmission electron microscopy (TEM) images a large-size immunogold-labelled GFP+ NPC within a cervical lymph node of a R-EAE mouse at 72 days after cell injection. These GFP+ cells display morphological and ultrastructural features similar to individual NPCs from neurospheres in vitro (see also Figure S3). The NPC (pseudocolor green) takes contact with four individual lymph node cells (pseudocolor orange). The NPC shows an irregular and invaginated nucleus (n) with a single nucleolus (nu), and its cytoplasm contains abundant organelles; B, Individual GFP+ NPCs establishing anatomical contacts with two GFP− lymph node cells–one of which (upper right) possesses the morphological characteristics of lymph blasts–through polarized microvilli (boxed area). Note the electrodense grain precipitates within the cytoplasm (arrows) and on the membrane (arrowheads and boxed area); C–E, NPCs in lymph nodes establish cell-to-cell contacts with lymph blasts through cytoplasmic expansions (C) or elongated intercellular junctions (D). Transplanted NPCs are occasionally found in deeper contact and enclosing resident lymph cells (E). Images refer to representative draining lymph nodes from R-EAE mice injected s.c. with NPCs at 3 and 10 dpi. Scale bars in A and B: 2 µm, in C and E: 1 µm, and in D: 500 nm.