Donor Vδ1(+) γδ T cells expand after allogeneic hematopoietic stem cell transplantation and show reactivity against CMV-infected cells but not against progressing B-CLL

γδ T lymphocytes play an important role in immune reactions towards infections and malignancies. In particular, Vγ9(–)Vδ1(+) T lymphocytes are thought to play protective antiviral roles in human CMV infection. Recently, Vδ1(+) T lymphocytes were proposed to also have anti- B-CLL reactivity. Here we report a case of 48-year-old man who received allogeneic stem cell transplantation for progressive B-CLL. Within one year after transplantation, lymphoma relapsed despite a dramatic increase of Vδ1(+) T cells in the patient’s blood. In vitro killing assays revealed activity of patient’s γδ cells against CMV target cells, but not against the relapsing lymphoma-cells. This argues for a contribution of Vδ1(+) cells in the immune reaction against CMV reactivation, but does not support a strong correlation of expanded Vδ1(+) T cells and favorable disease outcome in B-CLL patients.