Using an ELISPOT assay (which measures IFN-γ as a functional readout of CTL cytolytic activity), they further showed that these circulating anti-ALK CTLs from ALK-positive ALCL patients were cytolytically active with low activation threshold for effective lysis of ALK-positive lymphoma cells, conclusive of functional memory T-cells in ALCL patients. Here, ALK is linked to anaplastic large cell lymphoma.