The inhibitory effect of IgG antibody on IgE antibody level assayed by paper disc RAST was evaluated using mite (Dermatophagoides farinae, D.farinae) antigen. A significant positive correlation was found between the IgE and IgG antibody levels. The IgG antibody levels in mite allergic patients were significantly higher compared with those in controls. The IgG antibody levels in the treated group (house dust immunotherapy) were higher but showed no significant difference from those in the untreated group. The RAST values were elevated by removal and suppressed by addition of IgG antibody. These results suggested that in D.farinae allergic patients, the IgE antibody levels even from untreated patients when assayed by paper disc RAST indicates a lower level in the presence of IgG antibody or antibodies of other classes. Furthermore, antibody levels by this method are measured frequently with excess antibody. These factors may produce a difficulty in precise estimation of the seasonal variations in IgE antibody levels or suppression of IgE antibody levels after immunotherapy. The preciseness of quantification by this method may be improved by the use of diluted serum, which is simple and preferable for miminization of the effect of the above 2 factors.
