8-Hydroxyguanosine and 8-methoxyguanosine possess immunostimulating activity for B lymphocytes.

The present paper extends previous observations of Goodman and Weigle (M.G. Goodman and W.O. Weigle, J. Immunol. 128, 2399, 1982) and describes the activation of B lymphocytes by a number of C-8-substituted guanine ribonucleosides. 8-Hydroxyguanosine stimulates both proliferation and differentiation of murine B cells while 8-methoxyguanosine stimulates only differentiation and 8-aminoguanosine has no discernible effect on B-cell activation. The former two compounds also increase the magnitude of the antibody response to the type 2 antigen trinitrophenyl-AECM-Ficoll. These data demonstrate that guanosine, which is itself inhibitory to murine B cells, is converted into an immunostimulatory molecule after substitution at its C-8 position with methoxy or hydroxy groups and the bromo or mercapto group not essential for conferring biological activity to this nucleoside. However, our data also suggest that substitution of different groups at the C-8 position does influence the biological activity of this molecule.