Phase 2 Trial of Prophylactic Rituximab Therapy for Prevention of CGVHD

Recipient Inclusion Criteria:

* Between 18 and 76 years of age
* Chronic lymphocytic leukemia (CLL):

  * Unmutated IgG VH gene status
  * Mutated IgG VH genes (\> 2% nucleotide change compared to somatic sequence)
  * Complete remission benefit most from allogeneic hematopoietic stem cell transplant (HSCT).

(Physicians will be encouraged to provide aggressive chemotherapy prior to nonmyeloablative transplantation.)

* Mantle cell lymphoma (MCL): Transplant physicians believe subject would benefit from allogeneic HSCT.
* Adequate renal (Cr \< 2.4 mg/dL) and hepatic (Bilirubin \< 3.0 mg/dL, Aspartate aminotransferase (AST) \< 100 IU) function.
* Men and women of reproductive potential must agree to use an acceptable method of birth control during treatment and for six months after completion of treatment.
* All subjects must provide written informed consent

Donor Inclusion Criteria:

* Genotypically or phenotypically human leukocyte antigen (HLA)-identical.
* Age \< 76 unless cleared by institutional PI
* Capable of giving written, informed consent.
* Must consent to peripheral blood stem cell (PBSC) mobilization with G-CSF and apheresis

Recipient Exclusion Criteria:

* Recipient has a 9 of 10 or 10 of 10 HLA identical donor (high resolution molecular genotyping at HLA A, B, C and DrB1, and DQ)
* Pregnancy
* Lactating
* Serious uncontrolled infection
* HIV seropositivity
* Hepatitis B or C seropositivity
* Cardiac function: ejection fraction \< 40% or uncontrolled cardiac failure
* Pulmonary: Diffusing capacity - carbon monoxide (DLCO) \< 50% predicted
* Liver function abnormalities: elevation of bilirubin to ≥ 3 mg/dL and/or AST \> 100
* Renal: creatinine \> 2.4
* Karnofsky performance score ≤ 60%
* Patients with poorly controlled hypertension (systolic blood pressure \> 150 or diastolic blood pressure \> 90 repeatedly).
* Known life-threatening hypersensitivity to rituximab or other anti-B cell antibodies.
* Inability to comply with the allogeneic transplant treatment.
* Uncontrolled central nervous system (CNS) involvement with disease

Donor Exclusion Criteria:

* Identical twin to subject
* Contra-indication to subcutaneous G-CSF at a dose of 16 mg/kg/d for 5 consecutive days
* Serious medical or psychological illness
* Prior malignancy within the preceding five years, with the exception of non-melanoma skin cancers.
* HIV seropositivity