In situ detection by monoclonal antibody D-35.1 of cells infected with Marek's disease virus that interact with splenic ellipsoid-associated reticulum cells.

Immuno- and enzyme-histochemical staining procedures were used to investigate in vivo the interaction of Marek's disease virus (MDV) with splenic non-lymphoid cells. The newly developed monoclonal antibody D-35.1, which recognizes all three MDV serotypes, was used to study the localization of MDV at various times after intramuscular inoculation of 1-day-old chicks with MDV strain K. The D-35.1-positive cells were detected in the bursa of Fabricius, spleen, thymus, proventriculus, and cecal tonsils, and the number of chickens showing the cells increased between days 4 and 10. From day 21, the skin of the chickens contained D-35.1-positive feather follicles. The D-35.1 monoclonal antibody did not stain any cells in peripheral blood, nerves, kidney, and gonads at any time. In addition, D-35.1-positive cells were not detected in lymphoproliferative lesions in visceral organs and peripheral nerves. Double staining procedures on serial sections using monoclonal antibody CVI-ChNL-68.2, specific for splenic ellipsoid-associated reticulum cells, revealed that the majority of D-35.1-positive cells were situated in the peri-capillary sheath of reticulum cells at day 10. The sheath of cells detected by monoclonal antibody CVI-ChNL-68.2 was disrupted, and they were clustered around D-35.1-positive cells. These results support the hypothesis that ellipsoid-associated reticulum cells are involved in the early pathogenesis of Marek's disease.