CD19 and rheumatoid arthritis: In the case of diseases such as lupus or rheumatoid arthritis, where B cells produce autoantibodies that damage tissues, CAR-T cells directed against CD19 eliminate these pathogenic B cells; (2) stimulation of T Cell activation signaling, once the CAR-T cells attach to their target (e.g., CD19 in B cells), the CAR receptor activates a cascade of intracellular signaling in the T cells that results in their activation and proliferation.