CD28 and leukemia: To directly assess the functional capacity of TCRTg101 in mice with advanced leukemia, mononuclear cells were isolated from livers of leukemia-bearing mice 14 and 18 days following TCRTg101 adoptive transfer (13 to 17 days following C1498 cell challenge) and were restimulated ex vivo with anti-CD3 and anti-CD28 antibodies or phorbol 12-myristate 13-acetate (PMA) and ionomycin.