[Determination of the leukemia virus in the lymphocytes of sick cattle].

Experiments were carried out to establish the leukosis virus in lymphocytes from the peripheral blood of spontaneously infected cattle. The infected animals were detected by means of the agar gel immunodiffusion test in demonstrating the presence of leukosis virus antibodies. Lymphocytes were obtained from the blood of positively reacting animals, which were cultured at 37 degrees C for 3 to 5 days in a 'MEM' nutrient medium with the addition of 10 per cent fetal calf serum and antibiotics. The virus in the cell culture liquid was concentrated with ammonium sulphate and polyethylene glycol after which it was tested for antigenic properties. Parallel to this the lymphocytes were studied via the electron microscope prior to and after culturing. It was found that at culturing such lymphocytes the culture liquid contained the virus, which, after concentration exhibited antigenic properties in the agar gel immunodiffusion test, forming a precipitation line with a leukosis-positive serum. As found by the electron microscope there were in the lymphocytes prior to and after cultivation viral particles which proved similar to the leukotic 'C' type viruses with budding of the cell membrane that was characteristic of the bovine leukosis virus.