The pl antibody can detect the scfv region of most antigen CARs. We use it to detect the scfv of CD33 in our CD33 CAR-NK, and it can also be diluted with good results!
I used recombinant protein L from ACROS Biosystems to prepare gold conjugates for immunosensors and rapid quantification of human IgG and was able to detect 2.5 ng of Human IgG in less than 1 minute. I highly recommend this product for the detection and isolation of antibodies and Fab'2 fragments. I will definitely be ordering this item again.