Eosinophils in lymph nodes of cows infected by bovine leukaemia virus.

Prescapular lymph nodes from 109 animals positive to bovine leukaemia virus (BLV) were evaluated in this study. Lymph nodes of 81 animals (74.3%) showed an increased number of eosinophils (Eo) in a variety of pathological reactions. Eo counts in T-zonal hyperplasia (47 cases, 43.1%) and mixed hyperplasia (13 cases, 11.9%) were significantly higher (P < 0.05 and P < 0.01, respectively) than in the control group. Similarly, a significantly increased number of blood eosinophils (BEo) was observed in cows with diffuse infiltration by Eo in the lymph nodes as compared to the number of BEo in cows serologically positive to BLV but without morphological changes in the lymph nodes and in cows which were serologically negative (P < 0.05 and P < 0.01, respectively). The possible role of eosinophilic granulocytes in the regulation of immune response to enzootic bovine leukaemia (EBL) is discussed.