Hapten-specific IgE antibody responses in mice. VI. Selective enhancement of IgE antibody production by low doses of X-irradiation and by cyclophosphamide.

Exposure of BALB/c, A/J, and (BALB/c X A/J)F1 mice, which are IgE high responder animals, to total body x-irradiation ranging from 50 to 200 R resulted in a dose-dependent enhancement of the hapten-specific IgE antibody level as compared to unirradiated control mice. In contrast, anti-hapten antibody responses of the IgG class in these same animals were rarely enhanced, and when so, were of a lesser degree. This relatively selective augmentation of the IgE vs IgG antibody responses was observed in both unprimed and primed mice. By utilizing adoptive transfer systems, it was demonstrated that the enhancing effects of x-irradiation resulted from its action on the carrier-primed cell population and not upon the responding B cells or upon macrophages. The data presented herein suggest that this enhancement phenomenon is the result of the elimination of T cells (or their products) with suppressive functions and that these cells are neither dependent upon nor specific for the carrier antigen employed in the immunization. This hypothesis is given indirect support by the observations that treatment of the same strains of mice with cyclophosphamide, in doses known to abrogate suppressive T cell functions, resulted in a similar enhancing effect to that observed after low doses of x-irradiation. In addition an interesting difference between IgE and IgG precursor B lymphocytes was observed by the ability of IgE B cells to differentiate to the secretory state at a strikingly more rapid rate than IgG B lymphocytes when exposed to comparable T cell helper influences. These observations may provide important clues to the cellular mechanisms of the immune regulation of the IgE response and its relationship to allergic diseases.