Histopathology of the Thymus

Abstract

The thymus is a primary lymphoid organ that manifests dynamic physiological changes as animals age in addition to being exquisitely sensitive to stress and toxic insult. It is typically the first lymphoid tissue to respond to immunotoxic xenobiotics, with the first change being loss of cortical lymphocytes by apoptosis. This is followed by removal of the apoptotic cellular debris and, in the absence of recovery, may lead to loss of the cortico-medullary demarcation and organ atrophy. Nonneoplastic proliferative changes include focal lymphoid hyperplasia and proliferation of medullary epithelial cells, often with formation of ribbons, cords, or tubules. Thymomas are relatively rare tumors that exhibit a wide spectrum of morphologic types but do not metastasize. Thymic lymphomas are common in some mouse strains and can become leukemic with hematogenous spread throughout the body.

Plasma Osteopontin Modulates Chronic Restraint Stress-Induced Thymus Atrophy by Regulating Stress Hormones: Inhibition by an Anti-Osteopontin Monoclonal Antibody

“…It manifests dynamic physiological changes and is exquisitely sensitive to stress and toxic insult. It quickly responds to chemical and physical challenges, consequently leading to loss of cortical lymphocytes by apoptosis followed by organ atrophy (27). Our data demonstrate both that injection of OPN into OPN-deficient mice enhances the CRS-induced thymus atrophy and that injection of a specific anti-OPN mAb (2C5) into WT mice ameliorates stress-induced thymus atrophy; changes in CORT levels were also partially reversed.…”

Background data on NOD/Shi-<i>scid</i> IL-2Rγ^null mice (NOG mice)

“…However, the cause of death of the remaining 2 mice was unclear. Thymic lymphoma is known to occur in NOG mice (Kato et al, 2009) and wild-type mice (Pearse, 2006a), and was the only lethal tumor detected in the present study. Atypical lymphoid hyperplasia, which is generally said to have a possibility to progress to malignant lymphoma (Pearse, 2006a), was also detected only in one female killed as scheduled at 7 weeks of age.…”

“…Thymic lymphoma is known to occur in NOG mice (Kato et al, 2009) and wild-type mice (Pearse, 2006a), and was the only lethal tumor detected in the present study. Atypical lymphoid hyperplasia, which is generally said to have a possibility to progress to malignant lymphoma (Pearse, 2006a), was also detected only in one female killed as scheduled at 7 weeks of age. The present study showed that NOG mice could live at least up to 52 weeks of age with the survival rate of 95% in both sexes when they were kept under clean conditions set up for immune-deficient animals.…”

Efecto en la Estructura Histológica del Timo de Ratas Sprague-Dawley Tratadas con Trióxido de Arsénico

“…Según Schuurman et al (1992) y Elmore (2006), el timo es un órgano muy sensible a la exposición de inmunotóxicos y una disminución en su tamaño o en el peso de la glándula es a menudo uno de los primeros indicios en señalar el efecto de dicha toxicidad, tal como fue observado en este trabajo. Pearse (2006), señala que el daño producido por un inmunosupresor puede tener o no, un efecto morfológico perceptible en la disminución de la celularidad en la corteza, en el compartimento medular o bien en ambos compartimentos, siendo los dos últi-mos casos menos frecuentes. El tratamiento con trióxido de arsénico muestra que la pérdida de celularidad se produjo en ambos compartimentos, tanto en la corteza como en la médula, viéndose más afectado el compartimento medular (junto a la unión corticomedular) siendo probablemente la disminución del tejido medular la responsable de la atrofia del timo.…”