Studies on the relationship between serum colloidal reactions (ZTT and TTT) and IgG subclasses, especially IgG1 and IgG2

The relationship between zinc sulfate turbidity test (ZTT and thymol turbidity test (TTT), and IgG subclasses, especially IgG1 and IgG2, was studied. Serum colloidal reactions of specimens from patients with IgG-myeloma usually show abnormally high values in ZTT and low values in TTT. But in some cases, values in ZTT and TTT are both low, and in a few cases both values are abnormally high. In order to see the reason why IgG-myelomas are classified into these three groups according to serum colloidal reactions. IgG subclasses of monoclonal proteins (MPs) isolated by zone electrophoresis were determined by immunodiffusion with anti IgG-subclasses. Results revealed that IgG1-myeloma showed high ZTT and low TTT and IgG2-myeloma showed low ZTT and TTT. Only two out of our 29 cases with IgG-myeloma showed high ZTT and TTT. MP from one of them belonged to IgG1-kappa and that from the other to IgG2-lambda. We checked the relationship between turbidity tests and electrophoretic mobility of MP and also that between these tests and L-chains' type of MP, but did not find any relationship between them. These findings suggest that IgG1 innately reacts with ZTT but not with TTT, while IgG2 does not react with any of these tests. MP from cases showing high values in both ZTT and TTT may have a special idiotype.