Specific manipulative programming of lymphoid cells with RNA
T h e P h e n o m e n o n Early experiments in the transfer of specific immunity with viable lymphoid cells have stimulated numerous studies during the last two decades, focusing on the search and identification of the subcellular component(s) contained in or on presensitized lymphoid cells responsible for specific lymphoid cell conversions. In this regard, our laboratory has taken a special interest in the area of transfer of specific reactivity in immune systems, mainly focusing on hot-cold phenol extracts of ribonucleic acid (RNA) prepared from presensitized lymphoid cells. Ass~yable reactions have included tumor qell cytotoxicity in vitro (14), cell migration inhibition by specific antigen (13), lymphokine production (12), tumor immunotherapy (14), immunity in infectious diseases (9) and, presumably, antibody formation and/or idiotype expression in systems in vitro (2). RNA-converted cells react against various antigenic determinants that are associated with bacteria (9), fungi (12,13), tissue of normal or neoplastic origin (14), viruses (9), or protozoans (9). The validity and specificity of the RNA conversion phenomenon is also reinforced by the demonstrable transfer of cellular immunity to some esoteric, chemically defined immunogenic specificities that include e~ or e DNPoligolysines (I 1) or mono-(p-amino)-N-chloroacetyl-L-tyrosine (ARSNAT) (3). The experiments in programming immunologically competent lymphoid cells with RNA are deceptively simple. In reality, they are fraught with a myriad of technical problems that can easily influence the experimental results, not the least of which is the ubiquitous presence of RNase. One usually incubates mixtures of macrophages, T and/or B cells with RNA in vitro, washes the cells, and then exposes the converted cells to the original immunogen that was used to immunize the RNA donor animal. The amount of RNA used to accomplish these cellular conversions can range from as little as 12 i.tg in certain purified, isolated fractions, to nearly 500 I~g with whole, unfractionated quantities (8). In some experiments, RNA-converted cells can then be injected into syngeneic or allogeneic animals, which usually are challenged with the specific immunogen used to immunize the RNA donor.