Antigens present in poliovirus concentrates react with antibodies present in the serum of hyperimmunized monkeys to give type-specific precipitates. One or more bands of precipitate can be formed wherever such homotypic reactants, diffusing into an agar gel, meet in sufficient concentration and in equivalent proportions.
No qualitative differences have been detected between the type-specific reactions given by different strains of the same virus type; and no precipitates have been seen which could be called "group-specific." Non-specific precipitates have occasionally been observed.
Type-specific poliovirus precipitins are found in the serum of poliomyelitis patients. Their concentration has been measured by a standardized method. They tend to develop in parallel with neutralizing antibodies against the same virus type, increasing in amount during the first weeks of illness in those patients who show concurrent neutralizing antibody rises.
The precipitation reaction has proved valuable in the antigenic analysis of polioviruses. Its general adoption as a diagnostic procedure is perhaps unlikely; but it may be well worth applying for special purposes.