Dendritic Cell (DC)/Myeloma Fusions in Combination With Nivolumab in Patients With Relapsed Multiple Myeloma

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