Capturing resting T cells: the perils of PLL.

12 Mar 2018

To the editor — Full understanding of lymphocyte activation will require thorough characterization of the ‘resting’ state and how it changes. Surfaces coated with the cationic homopolymer poly-L-lysine (PLL) are widely used for total internal reflection fluorescence (TIRF) imaging of the organization of surface proteins on resting lymphocytes^1,2,3,4,5 because PLL is assumed to be inert. Here we found that PLL initiated T cell signaling and profoundly altered the activity of membrane proteins such as the T cell antigen receptor (TCR). Therefore, the emerging idea that receptors and signaling proteins cluster by default^1,2,3,4,5, which has been based mostly on studies of lymphocytes interacting with PLL-coated surfaces, needs reconsideration.