Bovine leukosis III. Relationship between lymphocytosis and DNA synthetic lymphocytes

The relationship between lymphocytosis and cell counts of lymophocytes synthesizing DNA in peripheral blood of 321 mature cows from two leukosis herds and a control herd and 11 cows with leukotic tumors was investigated. Only data from 20 control herd and 109 leukosis herd animals which remained persistently in either negative or suspect or positive hematological class on repeated bleedings were utilized. In the leukotic cattle these studies were limited to the terminal stages of the disease.A positive correlation was noted between the number of DNA synthesizing lymphocytes and lymphocytosis. Corresponding increases in peripheral blood lymphocytes and in the numbers of DNA synthesizing lymphocytes of leukotic cattle and animals of leukosis herds was attributed to impaired lymphocytopoiesis. The evaluation of the control herd and of the leukosis herds was not clear-cut on the basis of lymphocyte counts alone, although the differences were more clearly defined when the data from hematological studies and estimation of DNA synthesizing lymphocytes were evaluated. The Göttingen bovine leukosis key classification in conjunction with the estimation of DNA synthesizing cells was found to be a reliable procedure for the early recognition of the leukosis herds but not leukotic individuals.