A light and electron microscopic quantitative analysis of nerve-immune cell contacts in the gut-associated lymphoid tissue of the mouse colon.
Light microscopy (LM) histochemistry and transmission electron microscopy (EM) have been used to investigate the structural relationship between immunocompetent cells and enteric nerves in the gut-associated lymphoid tissue (GALT) of the mouse colon, i.e., a) the scattered immune cells in the lamina propria, b) the lymphoid follicles and c) the cryptopatches. Nerve-immune cell contacts have been quantified by LM, using the osmium-zinc iodide procedure for visualizing nerve fibers. Appositions of nerves to immune cells have been studied by EM when the distance between the immune cell plasma membrane and the neurilemma was 200 nm or less. In the diffuse GALT a), the LM incidence of nerve-lymph cell and nerve-plasma cell contacts has been calculated to be one and half and, respectively, three times greater than would be expected by chance alone (P < 0.0001 in both cases). EM showed close apposition of axonal varicosities, mostly containing 60 nm diameter dense-cored vesicles, to B lymphoblasts/immunoblasts or plasma cells. In isolated lymphoid follicles b), nerve-immune cell contacts were identified almost exclusively in the T-cell dependent parafollicular regions; the incidence of such contacts, calculated by LM, did not exceed expected theoretical values. By EM, apposition of nerve varicosities to small/middle-sized lymphocytes containing cytoplasmic lysosomal granules was seen sporadically. Examination of nerve-immune cell contacts in cryptopatches c), a recently identified extrathymic T-cell generating compartment, allowed recognition of a small proportion of nerve-lymph cell structural interactions, both at LM and EM. This study provides systematic quantitative data on the microanatomical relationship between enteric nerves and immune cells in the various GALT compartments. Findings suggest that such nerve-immune cell contacts might represent the structural foundation for communication between enteric nerves and the GALT.
Crivellato
E
E
Department of Medical and Morphological Research, Section of Anatomy, University of Udine, Italy. enrico.crivellato@drmm.uniud.it
Soldano
F
F
Travan
L
L
D000818:Animals; D002450:Cell Communication / Q000276:immunology; D003106:Colon / Q000276:immunology* / Q000648:ultrastructure*; D005260:Female; D007413:Intestinal Mucosa / Q000648:ultrastructure; D008221:Lymphoid Tissue / Q000648:ultrastructure*; D008297:Male; D051379:Mice; D015213:Neuroimmunomodulation; D009474:Neurons / Q000648:ultrastructure*; D010950:Plasma Cells / Q000648:ultrastructure*