HUMAN ANTI-TETANUS TOXIN PRECIPITATING AND CO-PRECIPITATING ANTIBODIES

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 45  (1) , 183-190
Abstract
A comparative study was made of human precipitating [PP] and co-precipitating [COP] anti-tetanus toxin antibodies. IgG COP antibody represented 10% of the total antibodies in the serum and had immunological and biological properties similar to those described for COP antibodies of other animal species. Human PP and COP antibodies had the same electrophoretic mobility and were localized in the same Ig fraction. By immunoprecipitation it was not possible to find antigenic differences between PP and COP antibodies. Both antibodies were localized in the IgG1 and IgG3 subclasses and neither were in the IgG4 subclass. Only the PP antibody can form insoluble complexes with antigen. The PP and COP antibodies agglutinated sensitized sheep red cells; only the PP antibody agglutinated human red cells. To obtain a positive reaction in passive cutaneous anaphylaxis 8-10 times more COP antibody was required. The PP antibody activated the complement system while COP antibody lacked this capacity. This difference in behavior could not be attributed to localization of both antibodies in different IgG subclasses. The PP and COP antibodies were cytophilic. Only the former activated phagocytosis and increased clearance of antigen from the blood; COP antibody does not fix complement. Competition between human PP and COP antibodies in opsonization was analyzed. Competition of both antibodies for the antigen depends on their respective amounts. The K = 0.18 diminished to 0.05 when the ratio of PP:COP antibody changed from 70:30 to 30:70. Since COP antibody was isolated from the sera of vertebrates other than man, then this antibody could play a role in some immune mechanisms. That this antibody could function univalently and block the antigen is proposed. This could facilitate chronic parasitic, bacterial and viral infections, tumor growth and other chronic infections.