Historical Aspects

Abstract

A central problem in the use of antibodies as a test reagent is the recognition that the antibody—epitope reaction has occurred; much more will be said about this later in the book. All early work with antibodies and bacteria was based on direct observation of the visible lattice or network formed from the cross-linking of bacterial cells by the bivalent antibodies previously invisible to the naked eye. The in vitro phenomenon of these agglutination and precipitation processes was known at the beginning of the twentieth century. It was realized early on that immune animal sera consisted of mixtures of binding capacities (i.e. polyclonal) and the in vitro use was largely confined to ‘typing’ (i.e. taxonomic allocation of) pure cultures of bacteria. The precipitation techniques of immunodiffusion and immunoelectrophoresis for soluble antigens in a semi-solid matrix became quite sophisticated and were used for detailed studies of the occurrence of particular antigens in bacteria. Agglutination reactions, i.e. those that occur when an antiserum cross-links to antigens fixed to the surface of a cell, are still widely used in the form of slide tests for serotyping bacteria; a degree of sophistication has been introduced with the use of latex particles, sometimes colour coded, as antibody carriers (see Section 5.8.2).