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There is considerable evidence that substances other than immunoglobulins can bind human Clq. Utilizing purified human Clq immobilized on polystyrene beads, we have demonstrated that polymerized human albumin (PHALB-125I) binds to human Clq in a direct binding assay. This interaction required a high degree of albumin polymerization as the percentage of binding was proportional to the polymer size and monomeric albumin was unreactive. Binding was species specific in the human Clq bound only human, and not xenogeneic, polyalbumins. Similarly, polymers of various other human plasma proteins were unreactive. To demonstrate that this interaction was not unique to immobilized Clq, soluble Clq was shown to inhibit PHALB-125I binding to solid phase Clq. Because aggregated IgG, poly(I):poly(C), dextran sulfate, polyglutamic acid, and polylysine have been previously shown to bind Clq, we used them in further blocking experiments and found them also to inhibit the interaction between Clq and PHALB. Anti-human Clq and, to a lesser extent, anti-PHALB antibodies inhibited the interaction. The Clq-PHALB binding was pH, ionic strength, and temperature dependent. In addition, human Clq was not observed to bind hepatitis B surface antigen (HBsAg) directly; however, in the presence of sufficiently polymerized human albumin a Clq-PHALB-HBsAg complex was formed. These interactions may be implicated in hepatocyte-HBsAg receptor function as well as in the host defense mechanisms involved in hepatitis B virus infection.
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
August 1981,
Gastroenterology,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
January 1984,
Proceedings of the National Academy of Sciences of the United States of America,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
January 1979,
Journal of medical virology,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
September 1985,
Journal of virology,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
March 1987,
European journal of immunology,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
November 1986,
Archives of pathology & laboratory medicine,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
November 1985,
Molecular immunology,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
August 1983,
Gastroenterology,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
January 1976,
Transfusion,
D R Milich, and
E D Papas, and
P K Bhatnagar, and
G N Vyas
March 1986,
Gastroenterology,
