Epratuzumab in Treating Patients With Non-Hodgkin's Lymphoma

DISEASE CHARACTERISTICS: * Histologically confirmed low-grade follicular B-cell non-Hodgkin's lymphoma * Small cleaved cell OR * Mixed cell * The following are ineligible: * Primary CNS lymphoma * HIV lymphoma * Richter's lymphoma * Bulky disease (any single mass greater than 10 cm) * Pleural effusion with positive cytology for lymphoma * Failed prior standard chemotherapy for non-Hodgkin's lymphoma * Refractory to at least 1 prior treatment with rituximab * Disease progression or failure to achieve objective response within 6 months of beginning rituximab therapy * At least 1 bidimensionally measurable lesion * At least 1.5 cm by CT scan NOTE: A new classification scheme for adult non-Hodgkin's lymphoma has been adopted by PDQ. The terminology of "indolent" or "aggressive" lymphoma will replace the terminology of "low", "intermediate", or "high" grade lymphoma. However, this protocol uses the former terminology. PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Karnofsky 60-100% * ECOG 0-2 Life expectancy: * At least 4 months Hematopoietic: * Absolute granulocyte count at least 1,500/mm\^3 * Platelet count at least 50,000/mm\^3 * Hemoglobin at least 8 g/dL * Transfusion independent Hepatic: * Bilirubin no greater than 1.5 times upper limit of normal (ULN)\* * Alkaline phosphatase less than 2 times ULN\* * AST less than 2 times ULN\* NOTE: \*Unless lymphoma-related Renal: * Creatinine no greater than 1.5 times ULN unless lymphoma-related Other: * No other malignancy within the past 5 years except squamous or basal cell skin cancer or carcinoma in situ of the cervix * No other serious condition or infection that would preclude study participation * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 3 months after study participation PRIOR CONCURRENT THERAPY: Biologic therapy: * See Disease Characteristics * At least 12 weeks since prior autologous stem cell transplantation * No prior radioimmunoconjugate therapies Chemotherapy: * See Disease Characteristics * No more than 4 prior treatment regimens * At least 4 weeks since prior chemotherapy Endocrine therapy: * At least 2 weeks since prior corticosteroids * No concurrent steroids Radiotherapy: * See Biologic therapy * At least 4 weeks since prior radiotherapy to target lesion Surgery: * At least 4 weeks since prior major surgery unless recovered Other: * At least 4 weeks since prior experimental therapies * No other concurrent investigational or therapeutic agents