Immunochemical variables affecting radioantigen-binding assays of antibody to Haemophilus influenzae type b capsular polysaccharide in childrens' sera

J Infect Dis. 1987 Oct;156(4):582-90. doi: 10.1093/infdis/156.4.583.


In radioantigen-binding assays for antibody to Haemophilus influenzae type b capsular polysaccharide, an apparent antibody concentration [( (["Ab"]) is assigned to test sera on the basis of binding equivalence to dilutions of standard adult antiserum. In childrens' sera, ["Ab"] can disagree between laboratories and between intralaboratory assays using different preparations of radioantigen. Immunochemical variables causing disagreement include the dilution of test serum at which ["Ab"] is assigned and the concentration and size distribution of radioantigen. Binding-dilution curves of many childrens' sera displayed shallower slopes than did the standard, thus ["Ab"] increased with dilution, particularly in low-binding sera. An increase in radioantigen concentration also raised ["Ab"]. Using larger-sized radioantigen raised the binding in standard and childrens' sera comparably and thus would not directly affect ["Ab"] but would raise ["Ab"] indirectly by increasing the serum dilution. These results are theoretically predicted if the affinity of childrens' antibodies are lower than that of the standard.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Bacterial / analysis*
  • Bacterial Capsules
  • Bacterial Vaccines / immunology*
  • Child, Preschool
  • Haemophilus Vaccines*
  • Haemophilus influenzae / immunology*
  • Humans
  • Immunoassay
  • Infant
  • Polysaccharides, Bacterial / immunology*
  • Reference Values


  • Antibodies, Bacterial
  • Bacterial Vaccines
  • Haemophilus Vaccines
  • Haemophilus influenzae type b polysaccharide vaccine
  • Polysaccharides, Bacterial