Inhibition by RNA of the Transfer Reaction Following Homograft Sensitization*

Abstract

Prior studies from this laboratory have shown that normal rabbit lymph node cells may be altered to a state resembling transplantation immunity by incubation with RNA extracted from the lymph nodes of a rabbit immunized by skin grafts. The present investigations were undertaken in order to determine whether or not immune lymph node cells from the recipient of skin homografts could be prevented from manifesting transplantation immunity by incubation with lymph node ribonucleic acid (RNA) from the homograft donor. As before the transfer reaction was employed as an assay of transplantation immunity. Immune cells were harvested from recipient lymph nodes draining a skin homograft and were divided into two equal aliquots. One aliquot was incubated at 37[degree]C for 15 minutes in 0.7[image] sucrose containing RNA extracted with phenol from lymph nodes of the homograft donor. The other aliquot was simultaneously incubated in 0.7[image] sucrose alone. Following incubation each aliquot was injected intradermally into opposite sides of the homograft donor. The immune cells incubated with sucrose alone consistently produced a transfer reaction whereas the cells incubated with donor RNA produced no reaction or a markedly diminished reaction. The same result was obtained with RNA from an indifferent rabbit, however, autologous RNA from immune recipient lymph nodes and RNA from rabbit liver did not inhibit the transfer reaction. Evidence for the incorporation of RNA by the lymph node cells during incubation was obtained by autoradiography of cells incubated with tritium labeled RNA.