Rituximab + Immunotherapy in Follicular Lymphoma

This research study is a Phase 1 clinical trial. Phase 1 clinical trials test the safety of an investigational intervention and also try to define the appropriate dose of the investigational intervention to use for further studies. "Investigational" means that the intervention is being studied. Utomilumab and avelumab are drugs which may stimulate the immune system against tumor cells. Because they activate the immune system, they are sometimes called immunotherapy drugs. The FDA (the U.S. Food and Drug Administration) has not approved utomilumab or avelumab for treatment of this cancer. Rituximab is approved by the FDA (the U.S. Food and Drug Administration) as a treatment option for this disease. The purpose of this research is to learn about the effects of combining the immunotherapy drugs utomilumab and avelumab with rituximab in follicular lymphoma. The investigators hope to learn how safe the combinations of treatments are for participants with follicular lymphoma.