8-Mercaptoguanosine

8-Mercaptoguanosine is an immunoadjuvant that affects the in vivo antibody response to the T-cell-independent antigen TNP-Ficoll. 8-Mercaptoguanosine enhances IgG1, IgG2, and IgG3 antibody responses, but has no effect on IgM antibody responses. 8-Mercaptoguanosine also enhances antibody responses to very weak antigens such as pneumococcal polysaccharide and restores antibody responses in immunodeficient xid mice that are non-reactive to TNP-Ficoll.