We hypothesized protecting CD8 cells from fratricide by genetically deleting CS1 would improve efficacy of CS1-CAR-T in myeloma however, using multiple methods to test this, we saw neither a decrease nor an increase in efficacy in ΔCS1-Luc90-CS1-CAR-T compared to Luc90-CS1-CAR-T. The gene discussed is SLAMF7; the disease is plasma cell myeloma.