Transfer of Heightened Immunity to Skin Homografts by Lymphoid RNA *

Prior studies from this laboratory have indi- cated that previously unstimulated lymph node cells may be altered to a state resembling trans- plantation immunity by incubation in vitro with ri- bonucleic acid (RNA) extracted from specifi- cally sensitized lymph nodes (2, 3). The assay of transplantation immunity used in these experi- ments was the transfer reaction of Brent, Brown, and Medawar (4), which is a delayed inflammatory reaction in the skin produced by the intradermal injection of immune cells into the animal against which the anticipated immune response is directed. Our finding that lymphoid RNA from an immunized animal may confer upon otherwise unsensitized lymph node cells the capacity to produce a transfer reaction has been confirmed by Clarke and Wilson (5) and more recently by others (6, 7).