Development and composition of lymphoid lesions in the spleens of Marek's disease virus-infected chickens: association with virus spread and the pathogenesis of Marek's disease

• Published in: Avian pathology 1999-06, Vol.28 (3), p.287-300
• Main Authors: Baigent, S.J, Davison, T.F
• Format: Article
• Language: English
• Subjects: chickens; Disease; immune response; immunocytochemistry; lesions; lymphocytes; Mardivirus; Marek disease; pathogenesis; Pathology; phenotype; Poultry; spleen; spread; strain differences; virus replication; Viruses
• ISSN: 0307-9457; 1465-3338
• DOI: 10.1080/03079459994786

Changes in lymphocyte distribution in spleens of Marek's disease virus (MDV) infected White Leghorn chickens of line 7(2) (MD susceptible) and line 6(1) (MD resistant) were studied by immunocytochemistry. Lymphocytes expressing the MDV antigen pp38 (predominantly B cells) were detected from 4 to 6 days post-inoculation (d.p.i.) but not at or after 8 d.p.i., and were more numerous in line 7(2). In line 6(1), infection resulted in depletion of B lymphocytes and an increase in T lymphocytes from 3 to 6 d.p.i., but no change in distribution of these cells. From 8 d.p.i., the B-dependent tissue began to recover and the T cells decreased in number. In line 7(2), infection caused a dramatic change in lymphocyte distribution, with formation of 'lymphoid lesions'. Diffuse, irregular patches of B lymphocytes, around the capillaries, became surrounded by large aggregates of TCRalphabeta1(+) CD8(+) and CD4(+) lymphocytes, bordered by a band of TCRgammadelta(+) lymphocytes. From 8 d.p.i., the B-dependent areas partially recovered, while TCRalphabeta1(+) CD4(+) and CD8(+) lymphocytes, potentially transformed, became extensively scattered throughout the spleen. We conclude that in line 7(2), replication and spread of MDV is more efficient and T cell responses in early infection are greater, favouring the tumour stage of the disease.