What detection strategies can be used to validate CAR expression?

CAR expression is performed using flow cytometry, in which various methods like protein L, anti-Fab antibodies, or target antigens themselves are used for detection. Among these options, using target antigens is generally preferred due to its high specificity and minimal background noise. The protein L method involves using a bacterial protein that binds to the kappa light chains of antibodies, including the scFv portion of CARs. Anti-fab antibodies specifically recognize the Fab portion of antibodies, which includes the antigen recognition domain of CARs. Using target antigens directly verifies that the CARs are correctly folded and expressed on the cell surface. For example, T cells that can be modified to express CAR are designed to selectively identify and interact with specific cancer cells, thereby enhancing the immune system's ability to target cancer for therapy.