Estradiol administration
To evaluate the effects of exogenous estradiol in vivo , estradiol administration was performed using BLV-infected cattle (animals #6–#10, Table 1). 2.5 mg/100 kg of estradiol benzoate (OVAHORMON INJECTION; Aska Animal Health, Tokyo, Japan) was inoculated intramuscularly, and peripheral blood samples were collected from these cattle before inoculation (Day 0) and at 1 and 6 hours and 1, 2, 3, 4, and 7 days after inoculation. PGE2 and estradiol concentrations in serum were measured by ELISA, as described above. Whole-blood culture and PBMC culture were conducted to evaluate BLV-nonspecific and BLV-specific Th1 responses, respectively.