RNA/nucleotide enhances antibody production in vitro and is moderately mitogenic to murine spleen lymphocytes.

Suppression of immune functions was demonstrated in both humans and animals when exogenous RNA was eliminated from the diet. However, direct actions of RNA/nucleotide on the immune system are virtually unknown. Thus, in this study, we explored effects of RNA and nucleotide on lymphocyte functions in vitro. Yeast whole RNA, which is free of endotoxin, was supplemented to culture media, and changes in mitogen responses, thymocyte proliferation, or in vitro antibody production by murine spleen lymphocytes were analyzed. Yeast whole RNA potentiated the proliferation of spleen lymphocytes and it also strikingly enhanced in vitro antibody production in response to sheep red blood cells at least 10-fold. However, it did not potentiate the proliferation of thymocytes (immature lymphocytes). These enhancing activities of yeast RNA were significantly reduced by RNAse treatment, but not by treatments with DNAse or polymyxin B. Certain mononucleotides exhibited less, but similar, action on murine spleen lymphocytes. The whole yeast RNA employed was already degraded to small nucleotide (less than 1 kb). Therefore, it may be suggested that certain components of RNA degraders can function as powerful immunomodulators, indicating that exogenous RNA or nucleotide may be important in facilitating immune responses under certain circumstances.