Mast cells in lymph nodes of cows infected by bovine leukaemia virus.

The number of mast cells (MCs) was determined in the prescapular lymph nodes of 109 animals seropositive to bovine leukaemia virus (BLV). The number of MCs was studied in relation to a variety of pathological reactions affecting lymph nodes. A significant increase of MCs was found in T zonal hyperplasia, B zonal hyperplasia, and mixed hyperplasia (P < 0.01) as compared to the control group. There was no significant increase in pulp proliferation and atrophy of the lymph nodes. MCs were mainly found in the medullary cords and sinuses. The possible role of MCs in the regulation of immune responses to enzootic bovine leukaemia (EBL) is discussed.