IGG AUTOREACTIVITIES AND POLYREACTIVITIES OF NORMAL HUMAN SERA

Using a panel of self antigens, IgM autoreactivities were clearly and constantly detected by enzyme immunoassay (EIA) in the sera of 29 norm al human individuals. Similarly, IgM autoreactivities in sera were rep roducibly detected by immunoblotting, using human organ extracts as th e antigen sources. In contrast, IgG reactivities were low in whole ser a but were considerably increased after affinity-chromatography purifi cation on protein G-Sepharose. These increases differed from one indiv idual IgG preparation to another and from one antigen to another (from 1-94 times) resulting in a unique IgG autoreactivity pattern for each subject. IgG reactivities diminished markedly when the IgG-depleted s erum was added to the isolated autologous IgG. IgM antibodies isolated from sera on F(ab')2 IgG immunoadsorbent partially inhibited the bind ing of IgG to tubulin and myosin but not to actin. The individual IgG preparations examined separately exhibited, with all the autoantigens of the panel, higher autoreactivities than those of the same-but-poole d IgGs, which in turn were higher than those of a commercially availab le human IgG preparation obtained from approximately 8,000 healthy don ors and used for intravenous injection. Depending upon the individual IgG sample, 31-65% of the IgG were bound to a DNP-Sepharose column and were eluted with DNP-glycine. The isolated anti-DNP antibodies were f ound to be polyreactive and possess higher autoreactivities than the o riginal IgG preparation for all the antigens of the panel. Similarly, IgG antibodies analysed using an antibody exchange procedure were foun d to be essentially polyreactive but some apparently monospecific anti bodies were also noted. These results suggest that the great majority of IgG present in normal humans are composed of polyreactive autoantib odies. IgG autoreactivities are only marginally expressed in these who le sera because of IgM-IgG, IgG-IgG and other, still unidentified, int eractions.