Allogeneic NK cells

This research study is for people who have relapsed or refractory B-cell non-Hodgkin's lymphoma (NHL) that has not responded to two or more lines of therapy. The purpose of this study is to identify the recommended dose of allogeneic NK cells in combination with IL-2, Tafasitamab and Rituximab for the treatment of relapsed or refractory B-cell non-Hodgkin's lymphoma. NK cells are an investigational (experimental) treatment which means they are not approved by the Food and Drug Administration (FDA). NK cells are a type of lymphocyte that's part of the body's natural immune system, and they can kill cancer cells by creating pores in the cancer cell membranes and inducing apoptosis (programmed cell death). Participants in this study will receive lymphodepleting chemotherapy, as well as Allogeneic NK cells, Tafasitamab and Interleukin-2 (IL-2) by an intravenous (IV) infusion. Participants are expected to complete one cycle, and they may be eligible to complete a second cycle of the same regiment if they have stable disease, partial or complete remission at the end of the first cycle. Participants will be in this study for about 12 months.