Inclusion Criteria:

          -  Histologically confirmed follicular lymphoma, grade 1-3a

          -  Patients who have relapsed after at least 1 prior anti-lymphoma therapy that include
             anti-CD20 monoclonal antibody and an alkylator chemotherapy agent, or at least 2 prior
             anti-lymphoma therapies that include anti-CD20 monoclonal antibody, may be included

          -  Anti-CD20 mAb-naïve or anti CD20 mAb-sensitive (defined as progression of FL ≥ 6
             months following prior anti-CD20 mAb containing therapy).

          -  Presence of measurable disease according to the 2014 Lugano Classification

          -  Disease course appropriate for therapy initiation approximately 4-5 months from
             enrollment per treating physician.

          -  Tumor site amenable to a) excisional biopsy or b) approximately 12 core biopsies from
             lymph node or extranodal site(s) or other site of lymphoma or c) other surgical
             procedure to provide adequate lymphoma sample for TSMA sequencing and screening.

          -  At least 18 years of age.

          -  Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1

          -  Normal bone marrow and organ function as defined below:

               -  Absolute neutrophil count ≥ 1,000/mcl

               -  Platelets ≥ 100,000/mcl

               -  Total bilirubin ≤ 1.5 x ULN

               -  AST, ALT ≤ 3.0 x ULN

               -  Creatinine clearance ≥ 50 mL/min (calculated by the Cockcroft-Gault or via
                  24-hour urine collection)

          -  Women of childbearing potential and men must agree to use adequate contraception
             (hormonal or barrier method of birth control, abstinence) prior to study entry and for
             the duration of study participation. Should a woman become pregnant or suspect she is
             pregnant while participating in this study, she must inform her treating physician
             immediately.

          -  Ability to understand and willingness to sign an IRB approved written informed consent
             document (or that of legally authorized representative, if applicable).

        Exclusion Criteria:

          -  Known current or previous histologic transformation from indolent non-Hodgkin lymphoma
             to diffuse large B-cell lymphoma or other aggressive lymphoma histology.

          -  Any anti-lymphoma treatment within 6 months' treatment initiation.

          -  Prior therapy with anti-PD-1, PD-L1, or PD-L2 agent.

          -  Diagnosis of a condition requiring systemic treatment with either corticosteroids (>
             10 mg daily prednisone equivalents) or other immunosuppressive medications within 14
             days of study drug administration. Inhaled or topical steroids and adrenal replacement
             doses > 10 mg daily prednisone equivalents are permitted in the absence of active
             autoimmune disease.

          -  Live vaccine within 30 days prior to treatment initiation.

          -  Prior organ allograft or allogeneic transplantation.

          -  Known central nervous system (CNS) involvement with lymphoma.

          -  Tested positive for hepatitis B surface antigen (HBV sAg) or hepatitis C virus
             ribonucleic acid (HCV antibody) indicating acute or chronic infection.

          -  Known history of HIV or AIDS.

          -  History of concurrent malignancy requiring active therapy or prior history of another
             malignancy within 5 years

          -  Active, known, or suspected autoimmune disease. Subjects are permitted to enroll if
             they have vitiligo, type 1 diabetes mellitus, residual hypothyroidism due to
             autoimmune condition only requiring hormone replacement, psoriasis not requiring
             systemic treatment, or conditions not expected to recur in absence of an external
             trigger.

          -  Currently receiving any other investigational agents.

          -  A history of allergic reactions or significant toxicity attributed to compounds of
             similar chemical or biologic composition to anti-CD20 mAbs, anti-PD-1 mAbs, or TLR
             agonists.

          -  Uncontrolled intercurrent illness including, but not limited to, ongoing or active
             infection symptomatic congestive heart failure, unstable angina pectoris, or cardiac
             arrhythmia.

          -  Women who are pregnant and/or breastfeeding. Women of childbearing potential must have
             a negative serum or urine pregnancy test within 24 hours prior to the start of
             nivolumab.