Semiquantitative Morphological Analysis of Stromal Cells the Irradiated and Recovering Rat Thymus.

Abstract

To understand the roles of thymic stromal cells in T-lymphocyte development, we semiquantitatively analysed rat thymi recovering from irradiation (6 Gy), using a transmission electron microscope. The most striking findings were that the percentage of subcapsular epithelial cells significantly increased in the cortex on day 3 after irradiation compared with the control; the percentage of intermediate epithelial cells significantly increased in the cortex on days 3 and 5 after irradiation and in the medulla on days 5 and 7 compared with the control; the interdigitating cells disappeared from the medulla by day 7 after irradiation and reappeared on day 9. The present data thus reveal that during recovery after irradiation (6 Gy), marked changes occur in the relative proportions of different epithelial cell subtypes in the cortex and medulla of the rat thymus. In addition, the percentages of macrophages and interdigitating cells also changed during the recovery. These changes, which may be associated with the abrupt proliferation of thymocytes after irradiation, should shed light on the significance of stromal cells in the T cell development.

Vanin-1−/− Mice Exhibit a Glutathione-Mediated Tissue Resistance to Oxidative Stress

“…Monitoring of ␥-irradiation-induced thymic depletion is another classical strategy to assess the radiosensitivity of an animal. On whole-body irradiation, the thymus undergoes a drastic involution involving thymocyte death and stromal cell disorganization; it is fully reconstituted by bone marrow precursor cell injection (2). This "depletion-regeneration" model is convenient to study postirradiation tissue repair (43).…”

MHC Class II Antigen Expression was Different from MHC Class I Antigen Expression in Irradiated and Recovering Rat Thymus.

“…1). Thymus weight started to recover on day 7, later than recovery from 600 R irradiation [2]. After 600 R irradiation, thymus weight started to recover on day 5.…”

“…The maximum decreases were observed on day 3 after irradiation [2,17]. These changes were rapidly repaired following abrupt proliferation of thymocytes.…”

“…On day 7 the vascular structure of the thymus had almost recovered [19], and the proportion of S-phase cells was 1.5 times greater than that of the normal control rats [8]. On day 14 the thymus mass had recovered to about 70% of normal [2,17], and the percentages of CD4 + CD8…”

“…We previously investigated the effects of radiation exposure on rat thymus at various doses [2,8,11,17,19]. In these studies, irradiation damaged not only thymocytes but also stromal components and vascular structures.…”