Leukocytes as carriers in the transmission of bovine leukemia: invasion of the digestive tract of the newborn by ingested, cultured, leukocytes
Kmetz, M.; Dunne, H.W.; Schultz, R.D.
American Journal of Veterinary Research 31(4): 637-641
1970
ISSN/ISBN: 0002-9645 PMID: 5437106 Document Number: 28342
leukocytes from milk were grown in vitro almost as readily as leukocytes from blood when bacterial contamination was controlled. Few differences were observed between cells cultivated from milk and those cultivated from blood of normal animals or between cells cultivated from normal and those cultivated from leucaemic cattle. Eagle's minimum essential medium in Hanks' balanced salt solution containing 35% bovine fetal serum and antibiotics provided an optimal medium for cultivation of the leukocytes. Leucocytes from the blood of both non-leucaemic and leucaemic cattle were grown on glass in stationary cultures. In general, the cultures were similar. Excessive manipulation caused condensation of nucleus and cytoplasm until leukocytes were reduced to almost half the diameter of the original cell. Leucocytes from non-leucaemic bovine blood adhered to glass in numbers of approx. 57 neutrophiles, 26 lymphocytes (all sizes), and 17 eosinophiles per 100 cells. In leukocyte cultures from leucaemic cattle, there were somewhat more lymphocytes and fewer eosinophiles and neutrophiles. Pale eosinophilic granules in the circumscribed cytoplasm of certain developing cells seemed associated with giant cell formation. Evidence was presented to strengthen the concept that Langhans' giant cell type can arise from multinuclear division within a cell. It seemed that in the cells described here, randomly distributed nuclei in a giant cell also may arise either from intracellular division of nuclei or by a rapid division and a "budding" process. Particles of approx. 130 m micro which closely resembled C-type virus particles of murine and feline leucaemia were observed in leukocytes obtained from the blood of a leucaemic cow and cultivated 4 days on glass. New-born mice were inoculated by mouth and s/c with cultured blood or milk leukocytes from two leucaemic cattle. Control mice included two non-inoculated groups and a group inoculated with cultured leukocytes from normal cattle. Splenomegaly was the predominant gross lesion in the mice after inoculation with cells from a donor leucaemic cow with extensive splenomegaly. There was no response in mice inoculated with blood or milk leukocytes from a second donor cow which subsequently died from generalized lymphosarcoma. Microscopic lesions in the mice included lymphoid infiltration and nodule formation in the lungs, liver, and kidneys, an increase in megakaryocytes, necrotic areas with a "starry sky" effect in lymph nodes, and hepatic cell proliferation. There was a higher incidence of lymphoid disease in the female mice. Bovine leukocytes were grown in vitro in fixed culture and labelled with trypan blue. When inoculated orally into colostrum-deprived, hysterectomy-derived rabbits, the labelled leukocytes appeared to penetrate into the mucosa of the upper digestive tract. Cells inhaled during oral inoculation appeared to be actively invading the alveolar tissue in the lungs. Failure of the cells to retain the dye in the digestive-tract epithelium limited the duration of the experiment.