INCLUSION CRITERIA:

        DISEASE CHARACTERISTICS:

          -  Confirmed diagnosis of B-cell non-Hodgkin's lymphoma

          -  Measurable disease

          -  Evidence of CD22-positive malignancy by the following criteria,

               -  > 30% of malignant cells from a disease site CD22+ by FACS analysis or,

               -  > 15% of malignant cells from a disease site must react with anti-CD22 by
                  immunohistochemistry

          -  Patients with indolent subtypes of CD22+ B-cell non-Hodgkin's lymphoma, including, but
             not limited to mantle cell lymphoma, follicular lymphoma and Waldenström's
             macroglobulinemia, are eligible if stage III-IV.

          -  Patients must have failed at least two or more courses of prior standard chemotherapy
             and/or biologic therapy (e.g. Rituxan). Patients with progressive mantle cell lymphoma
             may be eligible if they have failed one prior standard therapeutic regimen.

        PATIENTS CHARACTERISTICS

        Performance Status

          -  ECOG 0-2

        Life Expectancy

          -  Life expectancy of less than 6 months, as assessed by the principal investigator

        Other

          -  Patients with other cancers who meet eligibility criteria and have less than 5 years
             of disease free survival will be considered on a case-by-case basis

          -  Must be able to understand and sign informed consent

          -  Female and male patients must agree to use an approved method of contraception during
             the study

        Exclusion Criteria:

          -  History of bone marrow transplant

          -  Documented and ongoing central nervous system involvement with their malignant disease
             (history of CNS involvement is not an exclusion criterion)

          -  Pregnant or breast-feeding females

          -  Patients whose plasma contains either a significant level of antibody to CAT-8015 as
             measured by ELISA, or antibody that neutralizes the binding of CAT-8015 to CD22 as
             measured by a competition ELISA.

          -  HIV positive serology (due to increased risk of severe infection and unknown
             interaction of CAT-8015 with antiretroviral drugs)

          -  Hepatitis B surface antigen positive

          -  Uncontrolled, symptomatic, intercurrent illness including but not limited to:
             infections requiring systemic antibiotics, congestive heart failure, unstable angina
             pectoris, cardiac arrhythmia, psychiatric illness, or social situations that would
             limit compliance with study requirements

        Hepatic function: serum transaminases (either ALT or AST) or bilirubin

          -  ≥ Grade 2, unless bilirubin is due to Gilbert's disease

        Renal function: Serum creatinine clearance ≤ 60mL/min as estimated by Cockroft-Gault
        formula

        Hematologic function:

          -  The ANC < 1000/cmm, or platelet count <50,000/cmm, if these cytopenias are not judged
             by the investigator to be due to underlying disease (i.e. potentially reversible with
             anti-neoplastic therapy).

          -  A patient will not be excluded because of pancytopenia ≥ Grade 3, or erythropoietin
             dependence, if it is due to disease, based on the results of bone marrow studies

          -  Baseline coagulopathy > Grade 3 unless due to anticoagulant therapy.

        Pulmonary function:

          -  Patients with < 50% of predicted forced expiratory volume (FEV1) or <50% of predicted
             diffusing capacity for carbon monoxide (DLCO), corrected for hemoglobin concentration
             and alveolar volume. Note: Patient with no prior history of pulmonary illness are not
             required to have PFTs. FEV1 will be assessed after bronchodilator therapy.

        Recent prior therapy:

          -  Cytotoxic chemotherapy, corticosteroids (except stable doses of prednisone), whole
             body electron beam radiation therapy, hormonal, biologic or other standard or any
             investigational therapy of the malignancy for 3 weeks prior to entry into the trial

          -  Less than or equal < 3 months prior monoclonal antibody therapy (i.e. rituximab)

          -  Patients who are receiving or have received radiation therapy less than 3 weeks prior
             to study entry will be not be excluded providing the volume of bone marrow treated is
             less than 10% and also the patient has measurable disease outside the radiation port

          -  Any history of prior pseudomonas-exotoxin immunotoxin (PE) administration.