Autologous MHC-dependent leukaemia-reactive T lymphocytes in a patient with chronic myeloid leukaemia.

We have investigated the presence of T cells capable of recognizing autologous leukaemia cells in a patient with CML. We demonstrated that these cells were anergic to the leukaemia cells. They were estimated to be present at a frequency of 1:4000 T cells in the peripheral blood. However, following incubation with high dose rIL-2, these effector cells were able to proliferate, secrete TH1 cytokines and lyse target cells upon challenging with fresh autologous leukaemia cells. Both CD4 and CD8 T cells were involved in the proliferative responses. Moreover, the immune response was blocked by monomorphic anti-HLA antibodies, suggesting that the MHC molecules are needed by the T cells for leukaemia cell/antigen recognition. This work therefore indicates a potential reservoir of effector cells in CML patients which may be exploited for the modulation of leukaemia cell growth. It also provides evidence for a distinct T cell population capable of mediating GVL responses.