OBJECTIVES: I. Determine the objective response rate in patients with previously treated stage I, II, III, or IV low- or intermediate-grade B-cell non-Hodgkin's lymphoma treated with denileukin diftitox. II. Determine the time to progression, duration of remission, and time to treatment failure in patients after treatment with this therapy. III. Determine the toxicity of this therapy in these patients. IV. Correlate the results of the inteleukin-2 receptor assay with treatment outcomes in these patients.