Abstract
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 differentiated cells to an organ using embryonic stem cells, and the enhancement of the immune response using effector lymphocytes. In most cases, these cells must be injected systemically. Unfortunately, ex vivo manipulation or activation 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 deformability generally have adverse side effects on the therapeutic potential of the cells. Using micropipet aspiration techniques, cytotoxicity assays and in vivo trafficking studies we show that: (1) the rigidity of injected effector cells directly affects resistance to passage through tissue; (2) modulation 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, reduces cell rigidity and entrapment in the lungs.