Inclusion Criteria

DISEASE CHARACTERISTICS: Polyclonal or monoclonal B-cell lymphoproliferative disorder
while under pharmacologic immune suppression for control of either allograft rejection or
autoimmune disease Measurable disease as defined by one of the following: At least 1 tumor
mass measuring 1.0 cm in largest dimension Greater than 25% marrow involvement
Quantifiable extranodal disease Expression of CD20 antigen confirmed by biopsy or fine
needle aspirate Progression of disease or stable disease following reduction of
immunosuppressive medication and antiviral therapy Inability to further reduce
immunosuppressive medication

PATIENT CHARACTERISTICS: Age: 3 to 70 Performance status: Karnofsky 70-100% Life
expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,000/mm3
Platelet count at least 50,000/mm3 Hepatic: Not specified Renal: Not specified
Cardiovascular: No congestive heart failure Pulmonary: No pneumonitis Other: Not pregnant
or nursing Negative pregnancy test Fertile patients must use effective contraception
during and for 3 months after study No serious nonmalignant disease No active uncontrolled
bacterial, viral, or fungal infections

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks
since prior chemotherapy (6 weeks for nitrosoureas) No concurrent chemotherapy Endocrine
therapy: At least 2 weeks since change in dosing and type of immunosuppressive drugs
unless due to progression of disease Radiotherapy: At least 4 weeks since prior
radiotherapy No concurrent radiotherapy Surgery: At least 4 weeks since prior major
surgery (except diagnostic surgery) Other: At least 30 days or 5 half-lives since other
prior investigational drugs or whichever is longer