Inclusion Criteria:

          -  Patients must have Patients with relapsed multiple myeloma with prior treatment of an
             IMID and proteasome inhibitor.

          -  Age ≥18 years.

          -  ECOG performance status ≤2

          -  Patients must have > 20% plasma cells in the bone marrow aspirate differential <30
             days prior to enrollment.

          -  ANC > 1000; Platelets > 75K without transfusional support

          -  Participants must have normal organ function as defined below:

               -  total bilirubin ≤1.5 × institutional upper limit of normal

               -  AST(SGOT)/ALT(SGPT) ≤3 × institutional upper limit of normal

               -  creatinine clearance ≥40 mL/min/1.73 m2 for participants with creatinine levels
                  above institutional normal.

          -  The effects of DC/MM fusion and nivolumab on the developing human fetus are unknown.
             For this reason, women of child-bearing 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 she or her partner is participating in this study, she
             should inform her treating physician immediately. Men treated or enrolled on this
             protocol must also agree to use adequate contraception prior to the study, for the
             duration of study participation, and 5 months after completion of treatment.

          -  Ability to understand and the willingness to sign a written informed consent document

        Exclusion Criteria:

        -Participants who are receiving any other investigational agents.

        3.2.2 Patients with purely non-secretory MM [absence of a monoclonal protein (M protein) in
        serum as measured by electrophoresis and immunofixation and the absence of Bence-Jones
        protein in the urine defined by use of conventional electrophoresis and immunofixation
        techniques and the absence of involved serum free light chain >100 mg/L]. Patients with
        light chain MM detected in the serum by free light chain assay are eligible.

          -  Patients with Plasma Cell Leukemia

          -  Because of compromised cellular immunity, patients who have a known human
             immunodeficiency virus (HIV), active hepatitis C virus (HCV) or active hepatitis B
             virus (HBV).

          -  Myocardial infarction within 6 months prior to enrollment or New York Heart
             Association (NYHA) Class III or IV heart failure (see Appendix H), uncontrolled
             angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence
             of acute ischemia or active conduction system abnormalities. Prior to study entry, any
             ECG abnormality at screening will be documented by the investigator as not medically
             relevant.

          -  Active or prior documented autoimmune or inflammatory disorders including but not
             limited to the following:

               -  GI Disorders: (including inflammatory bowel disease [e.g. ulcerative colitis,
                  Crohn's disease], diverticulitis (with the exception of a prior episode that has
                  resolved), celiac disease, or other serious gastrointestinal chronic conditions
                  associated with diarrhea.

               -  Systemic lupus erythematosus

          -  Wegener's syndrome [granulomatosis with polyangiitis]

               -  Myasthenia gravis

               -  Graves' disease

               -  Rheumatoid arthritis

               -  Hypophysitis

               -  Uveitis

          -  The following are exceptions to this criterion: subjects with vitiligo or alopecia;
             subjects with hypothyroidism (e.g. following Hashimoto syndrome) stable on hormone
             replacement; or subjects with psoriasis not requiring systemic treatment.

          -  Individuals with a history of a different malignancy are ineligible except for the
             following circumstances. Note: Individuals with a history of other malignancies are
             eligible if they have been disease-free for at least 5 years and are deemed by the
             investigator to be at low risk for recurrence of that malignancy. Individuals with the
             following cancers are eligible if diagnosed and treated within the past 5 years:
             non-invasive cancer (such as, any in situ cancers) and basal cell or squamous cell
             carcinoma of the skin.

          -  Female patients who are pregnant (positive β-HCG) or breastfeeding

          -  Prior organ transplant requiring immunosuppressive therapy.

          -  Patients who previously received PD-1 antibody and have experienced toxicities
             resulting in treatment discontinuation.

          -  Uncontrolled intercurrent illness including, but not limited to, ongoing or active
             infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
             arrhythmia, or psychiatric illness/social situations that would limit compliance with
             study requirements