Summary
Chemotherapy plus rituximab has been the mainstay of treatment for follicular lymphoma (
FL
) for two decades but is associated with immunosuppression and relapse. In phase 2 studies, lenalidomide combined with rituximab (R
2
) has shown clinical synergy in front‐line and relapsed/refractory
FL
. Here, we show that lenalidomide reactivated dysfunctional T and Natural Killer (
NK
) cells
ex vivo
from
FL
patients by enhancing proliferative capacity and T‐helper cell type 1 (Th1) cytokine release. In combination with rituximab, lenalidomide improved antibody‐dependent cellular cytotoxicity in sensitive and chemo‐resistant
FL
cells, via a cereblon‐dependent mechanism. While single‐agent lenalidomide and rituximab increased formation of lytic
NK
cell immunological synapses with primary
FL
tumour cells, the combination was superior and correlated with enhanced cytotoxicity. Immunophenotyping of
FL
patient samples from a phase 3 trial revealed that R
2
treatment increased circulating T‐ and
NK
‐cell counts, while R‐chemotherapy was associated with reduced cell numbers. Finally, using an
in vitro
model of myeloid differentiation, we demonstrated that lenalidomide caused a reversible arrest in neutrophil maturation that was distinct from a cytotoxic chemotherapeutic agent, which may help explain the lower rates of neutropenia observed with R
2
versus
R‐chemotherapy. Taken together, we believe these data support a paradigm shift in the treatment of
FL
– moving from combination immunochemotherapy to chemotherapy‐free immunotherapy.