Response to antigenic determinants of Neisseria meningitidis lipopolysaccharide investigated with a new radioactive antigen-binding assay.

Adaptations of the Farr technique have resulted in a specific and reproducible radioactive antigen-binding assay for antibodies directed against the lipopolysaccharide (LPS) of Neisseria meningitidis. LPS was intrinsically labeled with 14C acetate during 16-hr growth in a modified Frantz media, extracted by hot phenol-H2O, and purified by dialysis, ultracentrifugation, and ethanol precipitation. LPS, which aggregates in aqueous solutions, was maintained in a monomeric form in 3% sodium deoxycholate (NaD) as determined by gel filtration on Sephadex G-75. Since NaD is insoluble in (NH4)2SO4, polyethylene glycol, 20%, was used to precipitate immunoglobulins of all three major classes.