Kinetics of the lymphocyte count in calves experimentally infected with BLV. Calves were experimentally inoculated with blood from an adult cow with PL. Absolute leukocyte counts were determined in heparinized blood samples using an automatic haematological analyser. Differential leukocyte counts were determined by visual observation of May–Gründwald–Giemsa-stained blood smears. Mean values ± standard errors are depicted. N = 6 calves with BoLA DRB3*1501, n = 6 calves with BoLA DRB3*0902 and n = 6 calves with neutral alleles.