USE OF PROTEIN-A-CONTAINING STAPHYLOCOCCUS-AUREUS AS AN IMMUNOADSORBENT IN RADIOIMMUNOASSAYS TO SEPARATE ANTIBODY-BOUND FROM FREE ANTIGEN

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 93  (4) , 614-621
Abstract
Heat-killed, formalinized Cowan I strain S. aureus (PASA) was examined for its utility as a solid-phase immunoadsorbent in various RIA [radioimmunoassay] procedures. Specific antibody could be adsorbed to PASA and then reacted with radiolabeled and unlabeled hormone or alternatively, PASA could be added to antibody-hormone mixtures to separate antibody-bound from free antigen. Both methods compared favorably with the more standard double-antibody method in each system tested. Antibodies produced by rabbits, guinea pigs, monkeys and humans were precipitated equally by PASA and double antibody, whereas antibody raised in sheep was precipitated much less by PASA than by double antibody. Antibody bound to PASA reached equilibrium of binding more slowly than unbound antibody for both rapid (TRH [thyrotropin-releasing hormone]) and slow (rPRL [rat prolactin]) reactions. Binding of free or complexed Ig[immunoglobulin]G by PASA was extremely rapid, reaching equilibrium in < 30 s. This rapid binding was utilized in kinetic experiments which would not have been possible with slower-reacting precipitating agents. The versatility permitted by this property constitutes one of the most useful characteristics of PASA. Other important attributes of PASA include its convenience, economy and wide applicability.