Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed refractory or recurrent hairy cell leukemia

- Relapsed after less than 2 years of complete remission after purine analog
therapy

- Must have at least one of the following indications for therapy:

- Progressive or massive splenomegaly

- Cytopenia defined by the following:

- Absolute neutrophil count less than 1,000/mm^3 OR

- Platelet count less than 100,000/mm^3 OR

- Hemoglobin less than 12 g/dL

- More than 20,000 hairy cells/mm^3

- Symptomatic adenopathy

- Constitutional symptoms including tumor-related fever or bone pain

- Evidence of CD22 positivity by 1 of the following:

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

- More than 30% of malignant cells from a site CD22+ by fluorescent-activated cell
sorter

- More than 400 CD22 sites/cell (average) on malignant cells as assessed by
radiolabeled anti-CD22 binding

- No CNS disease requiring treatment

- No patients whose serum neutralizes BL22 immunotoxin in tissue culture, due to either
antitoxin or antimouse-IgG antibodies

- No patients whose serum neutralizes more than 75% of the activity of 1
microgram/mL of BL22 immunotoxin

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 60-100%

Life expectancy:

- More than 6 months

Hematopoietic:

- See Disease Characteristics

- Pancytopenia due to disease allowed

Hepatic:

- ALT and AST less than 2.5 times upper limit of normal (ULN)

- Bilirubin less than 1.5 times ULN

Renal:

- Creatinine no greater than 2.0 mg/dL

Pulmonary:

- FEV1 at least 60% of predicted

- DLCO at least 55% of predicted

Other:

- HIV negative

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Prior bone marrow transplantation allowed

- At least 3 weeks since prior interferon for the malignancy

- More than 3 months since prior monoclonal antibody therapy (e.g., rituximab)

Chemotherapy:

- See Disease Characteristics

- At least 3 weeks since prior cytotoxic chemotherapy for the malignancy

Endocrine therapy:

- Not specified

Radiotherapy:

- At least 3 weeks since prior whole body electron beam radiotherapy for the malignancy

- Radiotherapy within the past 3 weeks allowed provided less than 10% of total bone
marrow was treated and patient has measurable disease outside the radiation port

Surgery:

- Not specified

Other:

- At least 3 weeks since prior retinoids for the malignancy

- At least 3 weeks since any other prior systemic therapy for the malignancy

- No concurrent therapeutic warfarin