Rituximab + Immunotherapy in Follicular Lymphoma

Inclusion Criteria: * Patients must have histologically determined follicular lymphoma, grade 1-3A, with pathologic review at the participating institutions, that has either: * Relapsed or primary refractory after at least one line of therapy including anti-CD-20 monoclonal antibody treatment (part A) or; * Has had no previous anti-lymphoma therapy other than corticosteroids or radiotherapy (part B). * Patients with active histologic transformation are excluded. Relapsed/refractory patients with prior transformation may be included as long as there is no evidence of transformation at the time of study entry by pathology, imaging, or clinical status * Patients in part B, without prior anti-lymphoma therapy, must be in need of treatment as defined by any of the following criteria: * Symptomatic adenopathy * Organ function impairment due to disease involvement, including cytopenias due to marrow involvement (WBC \<1.5x109/L; absolute neutrophil count \[ANC\] \<1.0x109/L, Hgb \<10g/dL; platelets \<100x109/L) * Constitutional symptoms * Maximum diameter of disease \> 7cm --\>3 nodal sites of involvement * Risk of local compressive symptoms * Splenomegaly (craniocaudal diameter \> 16cm on CT imaging) * Clinically significant pleural or peritoneal effusion * Leukemic phase (\>5x109/L circulating malignant cells) * Rapid generalized disease progression * Renal infiltration * Bone lesions * Patients may have had a prior autologous stem cell transplant and may have been treated with autologous chimeric antigen receptor T-cells (CAR T-cells). * Not in need of urgent cytoreductive therapy in the opinion of the investigator * Measurable disease that has not been previously irradiated on CT scans of at least 1.5 cm, OR if the patient has had previous radiation to the marker lesion(s), there must be evidence of progression since the radiation. Imaging must be completed no greater than 6 weeks prior to study enrollment. * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 (see Appendix A) * Adequate hematologic and organ function: * Absolute neutrophil count \> 1.0x109/L unless due to marrow involvement by lymphoma in which case ANC must be \>0.5x109/L * Platelets \> 75 x109/L, unless due to marrow involvement by lymphoma, in which case platelets must be \>50 x109/L * Creatinine \< 1.5 x ULN (upper limit of normal) or estimated GFR \> 40ml/min * Total bilirubin \< 1.5 X ULN, unless Gilbert syndrome, in which case direct bilirubin must be \< 3 x ULN * AST/ALT \< 2.5 X ULN, unless documented liver involvement by lymphoma, in which case AST/ALT must be \<5 x ULN * Age \>18 years * Ability to understand and the willingness to sign a written informed consent document. * Willingness to provide pre-treatment (or recent archival w/o intervening therapy), and on-treatment tumor samples by core needle or excisional surgical biopsy Exclusion Criteria: * Patients currently receiving anticancer therapies or who have received anticancer therapies within 28 days of the start of study drug (including chemotherapy, radiation therapy, antibody based therapy, etc.), or 56 days for radioimmunotherapy. Steroids for symptom palliation are allowed, but must be either discontinued or on stable doses of \< 10mg daily of prednisone (or the equivalent) at the time of initiation of protocol therapy. * Patients may not be receiving any other investigational agents, or have received investigational agents within 4 weeks (or 3 half-lives, whichever is longer) of beginning treatment. * History of severe allergic or anaphylactic reactions to monoclonal antibody therapy unless in consultation with an allergy specialist they are deemed eligible for retreatment with desensitization. * Patients who have previously received therapy with any drug that works by a similar mechanism of action as any drug being tested in a given cohort will be excluded from that cohort but will be allowed to enroll in other open cohorts. * Patients who have undergone prior allogeneic stem cell transplantation * Patients with a history of or active autoimmune disease (except controlled asthma, Hashimoto thyroiditis, atopic dermatitis, and/or vitiligo), or requiring systemic corticosteroids at a dose of 10mg prednisone equivalent daily. Patients with a history of autoimmune disease who never required corticosteroids and with no evidence of disease activity, and in whom the risk of reactivation is felt not to be serious, may be enrolled after discussion with the overall study chair. Exceptions to this are patients with a history of inflammatory bowel disease (ulcerative colitis and Crohn's disease). These patients are excluded regardless of whether their disease is active or inactive. * Patients with active pneumonitis or colitis, or patients with chronic liver disease and/or cirrhosis * Patients, who have had a major surgery or significant traumatic injury within 4 weeks of start of study drug, patients who have not recovered from the side effects of any major surgery (defined as requiring general anesthesia) or patients that may require major surgery during the course of the study. * Patients with known leptomeningeal or brain metastases. Imaging or spinal fluid analysis to exclude CNS involvement is not required, unless there is clinical suspicion by the treating investigator. * Patients with known HIV infection or hepatitis B or C infection. Testing for HIV is optional. Testing for hepatitis B and C is mandatory. Patients with hepatitis B core Ab positivity but negative surface antigen and negative viral load may be enrolled if they can be treated with a prophylactic agent (eg, entecavir); patients with hepatitis C seropositivity who have undergone successful treatment with negative viral load can also be enrolled. * Patients with a systemic fungal, bacterial, viral, or other infection not controlled (defined as exhibiting ongoing signs/symptoms related to the infection and without improvement, despite appropriate antibiotics or other treatment). * Prior history of another malignancy (except for non-melanoma skin cancer or in situ cervical or breast cancer) unless disease free for at least three years. Patients with prostate cancer are allowed if PSA is less than 1. * Patients should not have received immunization with attenuated live vaccine within one week of study entry or during study period. * Female patients who are pregnant or breast feeding, or adults of reproductive potential who are not using effective birth control methods. Women of child bearing potential (WOCBP) or male study participants of reproductive potential must agree to use double barrier birth control method of contraception during the course of the study treatment period and for 3 months after completing study treatment. WOCBP are defined as sexually mature women who have not undergone a hysterectomy or who are not postmenopausal (no menses) for at least 12 consecutive months. WOCBP must have a negative urine or serum pregnancy test within 14 days prior to administration of treatment. * History of noncompliance to medical regimens. * Patients who have any severe and/or uncontrolled medical conditions or other conditions that could affect their participation in the study such as: * New York Heart Association Class III or IV cardiac disease, including pre-existing clinically significant arrhythmia, congestive heart failure, or cardiomyopathy * Patients with a history of previous anthracycline treatment and are at risk of cardiac failure (New York Heart Association Class II or above) are excluded from cohorts A2, A3, and B2 (cohorts that include PF04518600) * Unstable angina pectoris, symptomatic congestive heart failure, myocardial infarction within 6 months of start of study drug, serious uncontrolled cardiac arrhythmia or any other clinically significant cardiac disease * Patients with any one of the following currently on or in the previous 6 months will be excluded from cohorts A2, A3, and B2 (any cohort that includes treatment with PF04518600) myocardial infarction, congenital long QT syndrome, torsade's de points, left anterior hemiblock (bifascicular block), unstable angina, coronary/peripheral artery bypass graft, cerebrovascular accident, transient ischemic attack or symptomatic pulmonary embolism or other clinically significant episode of thrombo-embolic disease\*. Ongoing cardiac dysrhythmias of NCI CTCAE grade \> 2, atrial fibrillation of any grade, or QTcF interval \>470msec at screening (except in case of right bundle branch block, these cases must be discussed with the principal investigator). \*Cases must be discussed in detail with the principal investigator to judge eligibility. Anticoagulation (heparin only, no vitamin K antagonists or factor Xa inhibitors will be allowed if indicated. * Other uncontrolled intercurrent illness that would limit adherence to study requirements