Agglutination assay for human opsonic factor using gelatin-coated latex particles

Check, I.J.; Wolfman, H.C.; Coley, T.B.; Hunter, R.L.

Journal of the Reticuloendothelial Society 25(4): 351-362

1979


ISSN/ISBN: 0033-6890
PMID: 313445
Accession: 004690621

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Abstract
A simplified assay for human opsonic .alpha.2-glycoprotein (opsonin) based on agglutination of gelatin-latex particles was developed and compared to a rat liver slice assay. Carboxy-latex beads covalently conjugated with gelatin by the carbodiimide reaction were used as test particles in place of the gelatinized colloidal lipid emulsion used by other investigators. The agglutination and liver slice assays yielded results which were quantitatively similar to each other and to those published by others who used the conventional liver slice assay. The particle-binding activity was specific for gelatin in that it could be inhibited by free gelatin, and particles coated with materials other than gelatin were not agglutinated. Agglutination required heparin and could be abrogated by protamine sulfate. Agglutinating activity was eliminated by preincubating serum for 1 h at 60.degree. C but not at 56.degree. C. Agglutination occurred more rapidly at 37.degree. C than at 22.degree. C, and was not observed at 0.degree. C. Opsonin levels in normal serum were lower than levels in normal plasma. The gelatin-conjugated carboxy-latex particles were stable over a period of at least several months.