Modulation of antigen-antibody complexations by immunoglobulins.

In this investigation, the modulating effects of non-immune human IgG and rheumatoid factors (RFs) on antigen-antibody complexations were studied. Non-immune human IgG, as well as RF, were found to inhibit the binding of antigen to specific antibodies of both human and rabbit origin. In addition, human immunoglobulins were also able to modify the composition of preformed antigen-antibody complexes. The effects were detected by immunological methods in two different antigen-antibody systems (human serum albumin-rabbit anti-HSA and tetanus toxoid-human anti-TT). Changes in biological activities could be followed by employing enzymes (glucose-6-phosphate dehydrogenase and human placental alkaline phosphatase) as antigens. The outcome of the effects was found to be dependent on the ratio of antigen to antibody, the antigen-binding properties of the antibody and its origin, and on the properties of the immunoglobulins added. The observed changes could not be explained only by the presence of specific antibodies in the immunoglobulin preparations. The ability of immunoglobulins to modulate antigen-antibody complexations may provide a rationale for the large amounts of non-specific immunoglobulins in the circulation by preventing premature precipitation and promoting the elimination of antigenic molecules.