Peptides derived from IgE heavy chain constant region induce profound IgE isotype-specific tolerance

(BALB/cxSJL)F1 mice, perinatally injected with peptide-N-glyconase F-treated, deglycosylated IgE heavy chain or recombinant IgE heavy chain (CHε2-CHε4), were profoundly inhibited in antigen-specific IgE production. There exist minimally two tolerogenic IgE peptides, residing in the CHε2 and CHε4 domains. Peptide I, generated by V8 protease, comprises 39 amino acids within CHε2, beginning at amino acid 103. Peptide E begins at amino acid 312 of the CHε 4 domain and extends through the CHε4 domain. The total lack of antigenspecific IgE responses in IgE peptide-treated mice was not due to overproduction of interferon-γ, nor lack of interleukin (IL)-4, as predicted by the Th2/IL-4 paradigm for IgE production. IgE-tolerant mice exhibited comparable levels of circulating anti-IgE antibodies to those of PBS-treated control mice. IgG obtained from sera of both sources failed to inhibit IgE responses in vitro. Moreover, IgE responses of spleen cells from IgE peptides-treated mice were restored by CD4⁺ T cells from PBS-treated control mice. We hypothesize that regulation of antigen-specific IgE responses is mediated by CD4⁺ T cells which normally recognize IgE peptides on IgE precursor B cells, and can be rendered tolerant by perinatal IgE peptide treatment.