Immune System

Thymus - Involution

    Narrative
    Thymus - Involution in a female Harlan Sprague-Dawley rat from a chronic study. The lymphocyte density is significantly decreased (arrow), and the corticomedullary junction is indistinct. Adipocytes infiltrate the capsule.
    Thymus - Involution in a female Harlan Sprague-Dawley rat from a chronic study (higher magnification of Figure 1). Small aggregates of plasma cells (arrows) are present within the medulla, and medullary epithelial cells are prominent.
    Thymus - Involution in a male Wister Han rat from a chronic study. Adipocytes infiltrate the periphery of the thymus, and the medullary regions are hypercellular (arrows).
    Thymus - Involution in a male Wister Han rat in a chronic study. A focal round area of B-cell hyperplasia is present in the medullary region (arrows).

    Authors

    Kristen Hobbie, DVM, PhD
    Principal Pathologist
    Huntingdon Life Sciences
    Peterborough, UK

    Susan A. Elmore, MS, DVM, DACVP, DABT, FIATP
    Staff Scientist, NTP Pathologist
    NTP Pathology Group
    National Toxicology Program
    National Institute of Environmental Health Sciences
    Research Triangle Park, NC

    Holly M. Kolenda-Roberts, DVM, PhD, DACVP
    Veterinary Pathologist
    SNBL USA
    Everett, WA

    Reviewers

    Jerrold M. Ward, DVM, PhD, DACVP, FIATP
    Veterinary Pathologist
    Global VetPathology
    Montgomery Village, MD

    Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
    Senior Pathologist
    Experimental Pathology Laboratories, Inc.
    Research Triangle Park, NC