JCAR014 and Durvalumab in Treating Patients With Relapsed or Refractory B-cell Non-Hodgkin Lymphoma

Inclusion Criteria: INCLUSION CRITERIA FOR SCREENING: * Relapsed or refractory diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS); high grade B cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements; primary mediastinal B-cell lymphoma (PMBCL); or DLBCL transformed from indolent histology with one of the following: * Persistent disease after first-line chemo-immunotherapy * Relapse after first-line chemo-immunotherapy and not eligible for autologous hematopoietic stem cell transplant (HCT) * Relapse or persistent disease after at least two lines of therapy or after autologous HCT * Ability to understand and provide informed consent INCLUSION CRITERIA FOR LEUKAPHERESIS AND PRE-THERAPY EVALUATION: * Screening evaluation appropriate for leukapheresis and T-cell collection * Evidence of CD19 expression on any prior or current tumor specimen or a high likelihood of CD19 expression based on disease histology INCLUSION CRITERIA FOR LYMPHODEPLETION CHEMOTHERAPY, JCAR014 AND DURVALUMAB: * Successful collection of T cells for JCAR014 manufacturing * Documentation of CD19 expression on any prior or current tumor biopsy * Internal review of histology * Detectable positron emission tomography (PET)-positive disease * Karnofsky performance status \>= 60% * Assessed by the investigator to have adequate bone marrow function to receive lymphodepleting conditioning chemotherapy * Serum creatinine \< 1.5 x age-adjusted upper limit of normal (ULN) * Alanine ami…