title: Ultrastructural and immunocytochemical studies of macrophages in an excitotoxin induced lesion in the rat brain.
abstract: An epidural application of kainic acid (KA) over the cerebral cortex in rat resulted in an extensive lesion in the ipsilateral cerebral cortex. This procedure elicited an accumulation of a large number of macrophages at the site of lesion covering a period of 4 weeks beginning 4 days after the KA application. The macrophages in the centre of lesion were characterized by abundant cytoplasm containing a variable number of lysosomes and phagosomes. Neurons at the same site were depleted during the period examined. They underwent degeneration following the KA treatment. With the monoclonal antibodies OX-42, OX-18 and OX-6, intense immunoreactivity was observed in these cells at the light and electron microscopic levels. Besides these antibodies, the cells were stained positively with the isolectin Griffonia simplicifolia (GSAI-B4). At the periphery of the lesion, many cells bearing the external morphology of microglia were also intensely stained with the GSAI-B4 and the monoclonal antibodies. It was concluded from this study that neuronal degeneration, caused by the excitotoxin KA, induced the accumulation of macrophages which exhibited CR3 receptors (marked by OX-42), MHC I antigen (marked by OX-18) and MHC Ia (marked by OX-6). The expression of these surface antigens may be related to their active phagocytic activity. The reaction with GSAI-B4 indicates the presence of specific lectin receptors on the macrophages which would serve a similar function. The present lectin histochemistry and immunohistochemical studies suggest that macrophages in the centre of the KA-induced lesion were derived from infiltrated monocytes while those at the periphery originated from the activation of local microglial cells.
authors.affiliation: Department of Anatomy, Faculty of Medicine, National University of Singapore.
authors.forename: C
authors.initials: C
authors.lastname: Kaur
authors.forename: Y G
authors.initials: YG
authors.lastname: Chan
authors.forename: E A
authors.initials: EA
authors.lastname: Ling
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001921:Brain / Q000187:drug effects / Q000276:immunology / Q000473:pathology*; D002540:Cerebral Cortex / Q000648:ultrastructure; D007150:Immunohistochemistry; D007608:Kainic Acid / Q000633:toxicity; D037102:Lectins; D008264:Macrophages / Q000187:drug effects / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D009410:Nerve Degeneration / Q000187:drug effects; D009498:Neurotoxins / Q000633:toxicity*; D037121:Plant Lectins; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000911:Antibodies, Monoclonal; C045475:Griffonia simplicifolia lectins; D037102:Lectins; D009498:Neurotoxins; D037121:Plant Lectins; D007608:Kainic Acid