Structural relationships between immune cells and longitudinal muscle during a Trichinella spiralis infection in the rat intestine

Abstract

A Trichinella spiralis infection produces an acute inflammatory reaction and tissue damage in the mucosa, and, in addition, functional changes occur in the external muscle layers. The aim of the present study was to characterize structural changes in the musculature that occur during early infection, and to identify relationships between immune cells and muscle cells, as part of an ongoing investigation into the immune modulation of motor function in the gut. Rats were infected with T. spiralis larvae and the gut fixed at 12 h, 24 h, 48 h and 6 days post-infection for electron microscopy of the longitudinal muscle. Macrophages and lymphocytes penetrated the longitudinal musculature 12-24 h post-infection. Distinct contacts were observed between specific cell types; cellular protrusions from macrophages or lymphocytes made close apposition contacts with smooth muscle cells. Resident macrophages in the subserosal space, fibroblast-like cells as well as smooth muscle cells showed marked activation during inflammation. Fibroblast-like cells were frequently seen intercalated between lymphocytes and smooth muscle cells, hence they may mediate communication between immune cells and the musculature.

Interstitial cells of Cajal, macrophages and mast cells in the gut musculature: morphology, distribution, spatial and possible functional interactions

“…However, ultrastructural studies of rat small intestine show macrophages located only between the mesothelial cells and LM [40, 77]. Furthermore, cross-sections as well as double staining with ED2 and KIT together with confocal microscopy confirm that the macrophages are located at the same three levels as in the mouse (Fig.…”

“…They are almost similar to one another with regard to their muscle layers, nerve plexuses, ICC networks and the location of macrophages. However, there are some differences between the two species in that the structure is simpler in mouse small intestine, where vessels are only found at AP and not in serosa [5], whereas in the rat both LM and serosa contain vessels [77]. In mice, other immune cells (B and T lymphocytes) – apart from an occasional mast cell – are absent [4, 73], but rat muscularis externa is also reported to contain neutrophils, mast cells, T-cells, natural killer cells and dendritic cells [39].…”

“…Enteric nematode infection is characterized by hypermotility and smooth muscle hyperplasia in muscularis externa [103] and an increased infiltration of immune cells: macrophages, lymphocytes, eosinophils and mast cells [77, 104, 105]. A recent study on Nippostrongylus brasiliensis infection found an increase in the number of infiltrated macrophages as well as in an up-regulation of.…”

“…In an immunohistochemical study on rat small intestine, macrophages (ED2 ϩ cells) were described within LM, between the muscle layers at the luminal side of the plexus and within CM [39]. However, ultrastructural studies of rat small intestine show macrophages located only between the mesothelial cells and LM [40,77]. Furthermore, cross-sections as well as double staining with ED2 and KIT together with confocal microscopy confirm that the macrophages are located at the same three levels as in the mouse (Fig.…”

“…Helminth infections induce a TH2 response, where macrophages can be alternatively activated by the TH2 cytokines in addition IL-10, arginase 1 and the mannose receptor (CD206) are up-regulated [24]. Enteric nematode infection is characterized by hypermotility and smooth muscle hyperplasia in muscularis externa [103] and an increased infiltration of immune cells: macrophages, lymphocytes, eosinophils and mast cells [77,104,105]. A recent study on Nippostrongylus brasiliensis infection found an increase in the number of infiltrated macrophages as well as in an up-regulation of.…”