Additional Study Information: You are being invited to take part in a research study that includes studying an experimental treatment named axicabtagene ciloleucel, referred to as axi-cel. The experimental treatment would involve removing some of your immune cells, genetically engineering those cells to identify cancer, receiving additional therapy while you wait for those cells to be released, and then infusing those cells back and assessing the effect on your cancer cells. The purpose of this main study is to determine if the experimental treatment, axi-cel, is safe and effective in treating your relapsed or refractory follicular lymphoma, compared to standard-of-care therapy. What treatment you receive will be randomly assigned (like tossing a coin), and you will have a 50% chance to receive axi-cel. You and your Study Doctor will know if you are receiving axi-cel or standard of care therapy. If you are randomized into the experimental treatment group, you will have one course of axi-cel treatment. Standard of care therapy may include Rituximab/Bendamustine (BR), Rituximab/Cyclophosphamide/Doxorubicin/Vincristine/Prednisone (R-CHOP), or Rituximab/Lenalidomide (R2) as selected by your Study Doctor.