CD4+ T cells orchestrate the immune response to ALK-positive T-cell lymphoma.

In a syngeneic mouse model of ALK+ anaplastic large cell lymphoma, CD4+ T cells are indispensable for driving and sustaining immunotherapy-induced antitumor responses.

• Why it matters: T-cell non-Hodgkin lymphomas are heterogeneous, and ICI mechanisms are hard to interpret because responses vary across subtypes, including reports of hyperprogression.
• What they did: The study used transplantation and immune-axis depletion in ALK+ ALCL mice, then tested ICI monotherapy and analyzed immune infiltration and T-cell states in primary human ALK+ ALCL samples.
• The result: PD-L1 blockade reversed regulatory T cell-mediated immunosuppression, increased circulating effector CD8+ T lymphocytes, and produced complete remissions in ∼50% of treated animals, while nonresponders showed exhausted CD4+ T cells with a T helper 22-like signature.

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