LYMPHOCYTE PROLIFERATION EFFICIENCY IN THE FIRST MONTHS OF LIFE OF HEIFERS NATURALLY INFECTED WITH BOVINE LEUKAEMIA VIRUS

The aim of the study was to determine the dynamics of changes in lymphocyte proliferation efficiency in the 1st months of life of heifers naturally infected with bovine leukaemia virus (BLV). Sixty-four Black-and-White breed heifers, originating from one herd, were examined. BLV infection was diagnosed with the ELISA and PCR test. The lymphocyte proliferation efficiency was determined using a lymphoblastic transformation test and isotope method. Phytohaemagglutinin (PHA) was used for the stimulation of the lymphocyte proliferation. The tests were performed in the 3 rd , 4 th , 5 th and 7 th month of life of the animals. When analysing the diversity of the lymphocyte proliferation efficiency, BLV infection did not have any effect on the blastogenic activity of PHA-stimulated and unstimulated lymphocytes in young heifers. However, the heifer age had a significant influence on the lymphocyte response to the mitogen. The weakest lymphocyte response to PHA was recorded in 3-month-old calves, regardless of BLV infection. The results seem to indicate that the activation of T cells and thus lymphocyte readiness to cellular response was lower in young heifers than in older animals. Moreover, the results suggest that the lymphocyte response to activation was similar in young BLV-positive and BLV-negative heifers.