We analyzed 38 untreated patients with chronic lymphocytic leukemia of B-cell type (B-CLL): 24 low-, 8 intermediate-, and 6 high-risk stage. In 15 patients (13 low risk and 2 intermediate risk), circulating Vδ1 T lymphocytes were significantly increased (100 to 300 cells/μL) compared with most intermediate, all high-risk stage, and 15 healthy donors (50 to 100 cell/μL). We studied these Vδ1 T lymphocytes and observed that they proliferated in vitro and produced tumor necrosis factor α or IFN-γ in response to autologous leukemic B cells but not to normal lymphocytes. However, they were unable to kill resting autologous B cells, which lack the MHC-related MIC-A antigen and express low levels of the UL16-binding protein (ULBP) 3 and undetectable levels of ULBP1, ULBP2, and ULBP4. All these molecules are reported ligands for the NKG2D receptor, which is expressed by γδ cells and activates their cytolytic function. The Vδ1 T lymphocytes studied were able to lyse the ULBP3+ C1R B-cell line upon transfection with MIC-A. More importantly, they also lysed autologous B-CLL cells when transcription and expression of MIC-A or upregulation of ULBP3 were achieved either by activation or by exposure to trans-retinoic acid. The NKG2D receptor expressed on Vδ1 T cells was involved in the recognition of B-CLL. Finally, in six patients with low numbers of circulating Vδ1 T cells and undetectable ULBP3, the disease progressed over 1 year, whereas no progression occurred in patients with high Vδ1 T lymphocytes and detectable/inducible ULBP3. These data suggest that Vδ1 T lymphocytes may play a role in limiting the progression of B-CLL.
ASJC Scopus subject areas
- Cancer Research