[Comparison of immunological activities of guinea pig IgG1 and IgG2 antibodies to low-molecular antigen].

The present study was carried out using a low-molecular antigen to clarify which of the two IgG subclasses (IgG1 and IgG2) of guinea pigs is responsible for the immunological assay systems in ordinary antigenicity tests for the development of a novel drug, and to what extent such IgG subclass antibodies contribute to the assay systems in addition to IgM antibody. Guinea pigs were immunized with TNBS plus FCA (3 mg/body), at intervals of 10 days, 3 times in total. The anti-TNBS serum was fractionated into peak I (IgG2), peak II (IgG1) and peak IV (IgM) by DEAE-cellulose column chromatography, and the immunological activities as well as the functions of the above three peaks were estimated by HA, homologous PCA reaction, PSANA and P-Arthus. The IgM and two IgG peaks possessed immunological activities on HA and P-Arthus, and the following degree of activities was shown in both assay systems: peak II (IgG1) greater than peak IV (IgM) greater than peak I (IgG2). In the homologous PCA reaction and PSANA, immunological activities were seen only in peak II (IgG1). It is confirmed that the IgG1 subclass is a homocytotropic antibody involved in the PCA and PSANA assay systems in the case of low-molecular immunogens such as TNBS.