Conversion of Non-Immune Rabbit Spleen Cells by Ribonucleic Acid of Lymphoid Cells from an Immunized Rabbit to Produce IgG Antibody of Foreign Light Chain Allotype

Abstract

Abstract Spleen cells (SpC) from non-immunized rabbits were converted to antibody “indirect” plaque-forming cells (PFC) by incubating them with ribonucleic acid (RNA) extracts of lymph node cells (LNC) obtained from rabbits 18 to 24 days after they were immunized with several intravenous injections of 4 × 108 sheep red blood cells (SRBC). The RNA extract was inactivated by ribonuclease (RNAse) but not by deoxyribonuclease (DNAse) or trypsin, indicating that the conversion required intact RNA. “Indirect” PFC were developed with optimal amounts of goat anti-IgG-Fc fragment and these were not inhibited by 2-mercaptoethanol (2-ME) or goat anti-IgM but were inhibited by excess anti-IgG-Fc fragment. This indicated that the antibodies produced by the PFC are of the IgG immunoglobulin class. The conversion was specific for the SRBC antigen injected. The light chain allotype of the IgG antibody produced by the PFC was identified by use of anti-b4 and anti-b5 to develop the “indirect” PFC, to visualize the PFC by radioautography and to inhibit plaque formation. Most of the “indirect” PFC of the converted SpC (64% to 84%) possessed IgG antibody with the allotype characteristic of the donor of the RNA extract; some of the “indirect” PFC (4% to 32%) possessed IgG antibody with the allotype characteristic of the donor of SpC. When the “RNA-converted” SpC were lysed by freezing and thawing, the anti-SRBC titer of the lysate, measured by the localized hemolysis in gel technique, was 4096 compared to 4 for lysates from the same number of lysed, nonimmune SpC alone. Moreover, anti-SRBC antibody could not be detected in the RNA extracts. These results indicate that a component of the RNA extract, presumably RNA itself, is providing information for the synthesis of at least part of the IgG antibody molecule.