A flow cytometric method for identifying Marek's disease virus pp38 expression in lymphocyte subpopulations

Identification of Marek's disease virus-infected lymphocytes is essential for a full understanding of the pathogenesis of Marek's disease. This paper describes the development of a simple, quantitative and reproducible flow cytometric technique for the identification of the phenotype of Marek's disease virus-infected lymphocytes. The method is based upon the detection of the Marek's disease virus-specific phosphoprotein pp38, in saponin-permeabilized lymphocytes, using the monoclonal antibody BD1, and the identification of the phenotype of pp38(+) lymphocytes using monoclonal antibodies against lymphocyte surface markers. pp38 expression in the spleen was demonstrated in the cytolytic phase of infection. The mean proportion of pp38(+) lymphocytes at 4 days post-infection was 0.43%. Of these, 95% were B lymphocytes, while only 4% were T lymphocytes (both CD4(+) and CD8(+)). The potential of the technique for the investigation of the cytolytic phase of Marek's disease is discussed.