Role of the spleen in the pathogenesis of Marek's disease.

The importance of the spleen for the pathogenesis of Marek's disease (MD) was investigated. The spleen was not required for infection of other organs or for the development of latently infected peripheral blood lymphocytes (PBL). Splenectomised (Sx) chickens had infected lymphocytes in the thymus, bursa and PBL by 6 or 7 days after intratracheal exposure to MDV. However, splenectomy did delay the spread of infection since intact birds had positive cells in these tissues 2 to 3 days earlier. Splenectomy reduced the number of visceral tumours in JM-10- but not in GA-5-infected chickens. Splenectomy did not influence the degree of protection by vaccination with SB-1.