One in five cats will develop cancer in their lifetime, and lymphoma is among the most common types of feline malignancies. Human chimeric antigen receptor (CAR) T cells have demonstrated remarkable success and have created strong interest translating this immunotherapy to companion animals. The Leifer lab developed the first-in-feline CAR T cells, and our long term objective is to create a CAR T therapy for feline lymphoma. However, progress has been hindered by lack of feline-specific reagents and challenges in obtaining suitable T cells for CAR T cell production. It is difficult to obtain enough healthy, non-malignant autologous T cells from cats with lymphoma to manufacture patient-specific therapies. Additionally, we do not have access to hybridomas against feline antigens, preventing us from cloning the antigen binding sequence of the antibody and making the CAR. To address these limitations, we propose to develop a chimeric antigen receptor against feline CD3 and develop artificial thymic organoids as a continuous source of feline T cells. Completion of these aims will establish the tools for an “off-the-shelf” feline CAR T cell products at an affordable cost.