Modulation of A-NK cell rigidity: In vitro characterization and in vivo implications for cell delivery

The delivery of cells to specific regions of the vasculature is a critical step in many therapeutic strategies. These include the packaging of DNA or RNA in cell "vehicles" for delivery to tissues, the reconstitution of diffe rentiated cells to an organ using embryonic stem cells, and the enhancement of the immune response using effector lymphocytes. In most cases, these ce lls must be injected systemically. Unfortunately, ex vivo manipulation or a ctivation can affect cell visco-elastic properties, making it difficult for the injected cells to traverse capillary beds. Compounding the problem is the fact that common agents used in the laboratory for increasing cell defo rmability generally have adverse side effects on the therapeutic potential of the cells. Using micropipet aspiration techniques, cytotoxicity assays a nd in vivo trafficking studies we show that: (1) the rigidity of injected e ffector cells directly affects resistance to passage through tissue; (2) mo dulation of cytoskeletal organization can be used to decrease cell rigidity , but can also compromise therapeutic efficacy; and (3) thioglycollate, an agent which does not influence effector lymphocyte cytotoxic activity, redu ces cell rigidity and entrapment in the lungs.