Effect of immunotherapy on immunoglobulin E and immunoglobulin G antibodies to ragweed antigens: A six-year prospective study

Abstract

The effect of immunotherapy with aqueous short ragweed (SRW) extract on IgE and IgG antibodies was tested over a 6 yr period in 47 adults with ragweed hay fever. Sera were collected each year in July and October from 1973 through 1979. In May 1976, 23 patients began immunotherapy with a lyophilized standardized SRW extract. From 1976 through 1979, treated patients received an average total dose of 4.8 × 10 3 protein nitrogen units (1039 μg of AgE). IgE antibodies to SRW and ragweed AgE were measured by the radioallergosorbent test (RAST) in antigen excess using allergens bound to Sepharose. Blocking antibodies primarily of the IgG class were measured by RAST interference. In response to inhalation of ragweed pollen, untreated patients showed seasonal rises (July to October) and postseasonal falls (October to July) of IgE antibodies during the entire study period. IgE antibody levels in the untreated patients decreased with time and from 1974 to 1979 fell 41% (p < 0.003) for an average halftime of 6.2 yr. Before immunotherapy, treated patients also showed seasonal rises and postseasonal falls. Treatment with SRW extract in 1976 produced an abrupt increase in IgE and IgG antibodies and a clear-cut suppression of seasonal rises of IgE antibodies without an effect on postseasonal falls through 1978. From 1974 to 1979, IgE antibodies to AgE and SRW decreased more in the immunized group than in the control group, and by 1979 these levels showed a mean fall of 73%. Blocking antibodies increased in the treated patients and reached maximal levels by July 1978. In 1978 and 1979, the levels of IgG blocking antibodies to AgE were inversely related to the IgE antibody levels to AgE. These results indicate that adults with ragweed hay fever show regular seasonal and postseasonal changes in IgE antibodies and that IgE antibodies spontaneously decrease with time. Immunotherapy magnifies these decreases by suppression of the seasonal rises, but it does not affect the postseasonal falls.