Induction of immunoenhancing factors for murine splenocyte cultures by Salmonella typhimurium ribosome and ribonucleic acid extracts.

Ribosomal and ribonucleic acid (RNA)-rich preparations derived from Salmonella typhimurium were examined for their ability to enhance the primary in vitro antibody response of normal mouse spleen cell cultures to sheep erythrocytes. Both of these fractions were consistently more active in elevating the antibody response of normal mouse splenocytes from lipopolysaccharide (LPS) responder mice than was LPS. Furthermore, injection of mice with either the ribosomal or RNA-rich fraction induced antibody response helper factor activity in 2-h post-treatment serum similar to that induced by LPS. Endotoxin low-responding C3H/HeJ mice were stimulated to release helper factors by ribosomes and the RNA extracts but not by LPS. Treatment of the ribosomes and RNA fractions with ribonuclease destroyed their ability to stimulate the production of the helper factor in serum of treated mice. Therefore, it appears likely that ribosomes and RNA-rich fractions stimulated an intermediate helper factor due to the presence of RNA and not LPS.