Inclusion Criteria:

          -  Histologically documented mantle cell lymphoma with co-expression of CD20 and CD5 and
             lack of CD23 expression by immunophenotyping and at least one of the following
             confirmatory tests: 1) positive immunostaining for cyclin D1; 2) the presence of
             t(11;14) on cytogenetic analysis; OR 3) molecular evidence of B-cell leukemia/lymphoma
             1 (bcl-1)/immunoglobulin heavy locus (IgH) rearrangement

               -  Cases that are CD5-negative and/or CD23-positive will be eligible provided that
                  the histopathology is consistent with mantle cell lymphoma AND positive for
                  cyclin D1, t(11;14), or bcl-1/IgH rearrangement

               -  A tissue block or unstained slides (10 - 20 slides) will be submitted to the
                  Roswell Park Cancer Institute (RPCI) Pathology Department for central pathology
                  review

               -  A diagnosis based on peripheral blood or bone marrow aspirate is allowed; if the
                  diagnosis is based only on blood, in addition to the immunophenotype and
                  molecular confirmation above, a peripheral blood smear must be available for
                  central pathology review; if the diagnosis is based on a bone marrow, the bone
                  marrow core biopsy or aspirate clot tissue block will be submitted to the RPCI
                  Pathology Department: if the tissue block is not available please submit the
                  diagnostic smears for review

          -  Extent of disease: stage I - IV; patients with nodular histology mantle cell lymphoma
             must have Ann Arbor stage III or IV disease to be eligible

               -  Patients with mantle zone type histology will not be eligible

               -  Patients with other mantle cell histologies are eligible regardless of stage

          -  Measurable or assessable disease is required; measurable tumor size (at least one node
             measuring 2.25 cm^2 in bidimensional measurement)

          -  No active central nervous system (CNS) disease defined as symptomatic meningeal
             lymphoma or known CNS parenchymal lymphoma; a lumbar puncture demonstrating mantle
             cell lymphoma at the time of registration to this study is not an exclusion for study
             enrollment

          -  Patients must be previously untreated

          -  No prior radiation therapy for mantle cell lymphoma

          -  >= 2 weeks since major surgery

          -  No known hypersensitivity to murine products

          -  No medical condition requiring chronic use of high dose systemic corticosteroids
             (i.e., doses of prednisone higher than 10 mg/day or equivalent)

          -  No human immunodeficiency virus (HIV) infection; patients with a history of
             intravenous drug abuse or any behavior associated with an increased risk of HIV
             infection should be tested for exposure to the HIV virus; patients who test positive
             or who are known to be infected are not eligible; an HIV test is not required for
             entry on this protocol, but is required if the patient is perceived to be at risk

          -  Non-pregnant and non-nursing; women and men of reproductive potential should agree to
             use an effective means of birth control

          -  Patients who test positive for hepatitis C antibody (Ab) are eligible provided all of
             the following criteria are met: 1) total bilirubin =< 2 x upper limit of normal; 2)
             AND aspartate aminotransferase (AST) =< 3 x upper limit of normal; AND 3) liver biopsy
             (pathology) demonstrates =< grade 2 fibrosis and no cirrhosis

          -  Specific guidelines will be followed regarding inclusion of MCL based on hepatitis B
             serological testing as follows:

               -  Hepatitis B surface antigen (HBsAg) negative, hepatitis B core antibody (HBcAb)
                  negative, hepatitis B surface antibody (HBsAb) positive MCL patients are eligible

               -  Patients who test positive for HBsAg are ineligible (regardless of other
                  hepatitis B serologies)

               -  For MCL patients with HBsAg negative, but HBcAb positive (regardless of HBsAb
                  status), should have hepatitis B virus (HBV) deoxyribonucleic acid (DNA) testing
                  done and protocol eligibility determined as follows:

                    -  If HBV DNA is positive the subject is excluded

                    -  If HBV DNA is negative, patient may be included but must undergo at least
                       every 2 months HBV DNA polymerase chain reaction (PCR) testing from the
                       start of treatment throughout the duration the study

                    -  Monitoring during the study is required at least every 2 months and during
                       follow-up at a minimum of every 2-3 months up to 6 months after the last
                       dose

                    -  Prophylactic antiviral therapy with lamivudine (3TC) or investigator's
                       preferred antiviral regimen throughout protocol therapy and for 6-12 months
                       thereafter may be initiated at the discretion of the investigator

                    -  If the patients' HBV DNA becomes positive during the study, the investigator
                       should manage the clinical situation as per the standard of care of
                       participating institution; the investigator should weigh the risks and
                       benefits of continuing ofatumumab or discontinuing ofatumumab before
                       appropriate treatment decisions are made for that individual patient

          -  Patients must not have a history of cardiac disease, defined as New York Heart
             Association class II or greater or clinical evidence of congestive heart failure (CHF)

          -  No known hypersensitivity to ofatumumab, humanized antibodies or chemotherapy agents
             throughout the protocol

          -  Left ventricular ejection fraction (LVEF) by multi gated acquisition scan (MUGA) or
             echocardiogram (ECHO) >= 45%

          -  Neutrophils > 1000/uL

          -  Platelets >= 75,000/uL (unless significant bone marrow involvement with MCL)

          -  Creatinine =< 2.0 mg/dL

          -  Total bilirubin =< 2.0 mg/dL (unless MCL related or attributable to Gilbert's disease)

          -  Urine or serum beta-human chorionic gonadotropin (HCG) or serum HCG = negative (if
             female patient of childbearing potential)

          -  Patient or legal representative must understand the investigational nature of this
             study and sign an Independent Ethics Committee/Institutional Review Board approved
             written informed consent form prior to receiving any study related procedure

          -  Consult with a physician experience in care and management of subjects with hepatitis
             B to manage/treat subjects who are anti-hepatitis B core antibody (HBc) positive

        Exclusion Criteria:

          -  Prior history of HIV-positivity (routine HIV testing is not required pre-treatment)

          -  Positive serology for hepatitis B (HB) defined as a positive test for HBsAg; in
             addition, if negative for HBsAg but HBcAb positive (regardless of HBsAb status), a
             hepatitis B DNA test will be performed and if positive the patient will be excluded

          -  Serious non-malignant disease (e.g., active uncontrolled bacterial, viral, or fungal
             infections) or other medical conditions (including psychiatric) which, in the opinion
             of the Principal Investigator (PI) would compromise other protocol objectives

          -  Presence of symptomatic CNS lymphoma

          -  Pregnant or lactating females

          -  Prior history of radiation or chemotherapy for MCL

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to ofatumumab or other agents used in study

          -  Patients with a "currently active" second malignancy, other than non-melanoma skin
             cancer or in situ carcinoma of the cervix or breast; patients are not considered to
             have a "currently active" malignancy if they have completed anti-cancer therapy, are
             considered by their physician to be at less than 30% risk of relapse and at least 2-5
             years have lapsed

          -  Major surgery, other than diagnostic surgery, within 2 weeks

          -  Patients with non-Hodgkin lymphoma (NHL) other than MCL

          -  Patients must not have a history of cardiac disease, defined as New York Heart
             Association class II or greater or clinical evidence of congestive heart failure; all
             patients must have a MUGA scan or 2-dimensional (D) echocardiogram indicating an
             ejection fraction of >= 45% within 42 days prior to registration; the method used at
             baseline must be used for later monitoring

          -  Unwilling or unable to follow protocol requirements

          -  Any condition which in the Investigator's opinion deems the patient an unsuitable
             candidate to receive study drug

          -  Received an investigational agent within 30 days prior to enrollment