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Enhanced Histopathology of the ThymusLaboratory of Experimental Pathology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA Correspondence: Address correspondence to: Susan A. Elmore, Laboratory of Experimental Pathology, NIEHS, NIH, 111 Alexander Drive, MD B3-06, Research Triangle Park, NC 27709, USA; e-mail:elmore{at}niehs.nih.gov The thymus is a primary or central lymphoid organ in which T lymphocytes undergo diffentiation and maturation autonomously within the cortex, without the need for antigenic stimulation, and it is essential for the normal development and function of the immune system. The thymus has been shown to be a sensitive target organ following exposure to immunotoxicants and endogenous corticosteroids, and a decrease in size or weight is often one of the first noted measures of compound-induced effects with cortical lymphocytes (thymocytes) being especially susceptible. Therefore, changes in thymus histopathology and architecture are considered to be of particular relevance for immunotoxicity screening. The separate compartments in each lymphoid organ should be evaluated separately and descriptive rather than interpretive terminology should be used to characterize changes within those compartments (Haley et al., 2005). Therefore, enhanced histopathological evaluation of the thymus involves the determination of the size and cellularity of the cortex and medulla, which should be noted separately. Other changes to evaluate include, but are not limited to, increased lymphocyte apoptosis, lymphocyte necrosis, cortex:medulla ratio and an increase or decrease in the epithelial component of the thymus.
Key Words: Apoptosis • cortex • medulla • tingible body macrophage • stress response
Toxicologic Pathology, Vol. 34, No. 5,
656-665 (2006) This article has been cited by other articles:
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