Detection of human autoantibodies specific for 5′-m⁷GMP and m⁷G(5′)ppp(5′)N

An enzyme-linked immunosorbent assay was utilized for the detection of spontaneously occurring antibodies with apparent specificities for m⁷G, 5′-m⁷GMP, and m⁷G(5′)ppp(5′)C. From the sera of 50 patients containing anti-nuclear antibodies, 48 (96%) possessed antibodies which bound to one or more immobilized nucleoside-BSA antigens (A-, G-, C-, U-, and T-BSA). Additionally, 8 (16%) of these sera contained immunoglobulins that reacted with m⁷G-BSA antigen. In these latter sera, soluble competitors such as m⁷G, 5′m⁷GMP, and m⁷G(5′)ppp(5′)C (but not 5′-AMP, -GMP, -CMP, -UMP, and -TMP or m¹G and m²²G) effectively inhibited antibody-binding to immobilized m⁷G-BSA. These results indicate the existence of spontaneously occurring anti-m⁷G antibodies in autoimmune diseases which are distinct from anti-G antibody populations.