Cellular immunity in Holstein cows seropositive for Bovine Leukosis Virus (BLV) during the transition period

ABSTRACT This research evaluated the dynamics of leukocytes and lymphocytes subsets in seropositive Holstein cows for BLV during the transition period. Blood samples (n=72) from 12 cows were harvested from week -2 up to week +3 to perform leukogram, immunophenotyping, cortisol and haptoglobin (Hp). Leukocytes pattern was characterized by leukocytosis, neutrophilia, monocytosis and eosinopenia around calving. Lymphocytosis and high proportions of B cells CD21+ were a constant finding between week -2 and +3, thus cows were tested and confirmed seropositive for BLV. The values of T lymphocytes subsets were low during the transition period, observing two peaks that coincided with high levels of cortisol at delivery (2.11µg/dL) and week +3 (1.97µg/dL). Hp had gradual increase from week -2 (166µg/mL) until week +3 (576g/mL) probably due to high rate of uterine infection detected between week +2 and +3. The seropositive cows for BLV presented stress leukogram around delivery, except for lymphocytes. Lymphocytosis and the high proportions of B cells, associated with the low proportions of T lymphocytes, can be indicative of immunosuppression and predisposition to the inflammatory process observed in the post-partum period.