Phenotype analysis of lymphocytes present in different stages of neoplasia induced by bovine leukemia virus.

Distribution of subpopulations of lymphocytes in the lymph nodes and tumor tissues from cattle with enzootic bovine leukosis (EBL) was examined by immunohistology using a panel of monoclonal antibodies against leukocyte differentiation molecules of bovine leukocytes and tumor-associated antigen (TAA) of EBL. As disease progressed in the lymph nodes, TAA positive cells increased in number and were strongly positive. The number of B-B2, IgM positive cells were reduced in frequency in the follicle and areas of neoplastic cell-proliferation. Alpha beta and gamma delta T cells positive for WC1 (workshop cluster designation) were reduced in frequency due to infiltration and proliferation of neoplastic cells. In tumor tissues which were thought to consist with monoclonal population of cells carrying BLV provirus, strongly TAA-positive cells were present throughout the section. Most of the neoplastic cells from five cattle with EBL appeared to be divided into four types, CD2-, CD4-, CD8-, WC1-, B2+ or B2-, IgM+ or IgM-, MHC II+ and strong TAA+. WC1+ cells played no apparent role in the development of lymphosarcoma of EBL. WC1+ cells were not observed in tumor tissues. However, the possibility of effect of T cell for tumor immunity was suggested, since TH/l and Tc/s cells were scattered in the tumor tissues.