A human IgE bispecific antibody shows potent cytotoxic capacity mediated by monocytes.

The generation of bispecific antibodies (bsAbs) targeting two different antigens opens a new level of specificity and, compared to mAbs, improved clinical efficacy in cancer therapy. Currently, the different strategies for development of bsAbs primarily focus on IgG isotypes. Nevertheless, in comparison to IgG isotypes, IgE has been shown to offer superior tumor control in preclinical models. Therefore, in order to combine the promising potential of IgE molecules with increased target selectivity of bsAbs, we developed dual tumor-associated antigen-targeting bispecific human IgE antibodies. As proof of principle, we used two different pairing approaches - knobs-into-holes and leucine zipper-mediated pairing. Our data show that both strategies were highly efficient in driving bispecific IgE formation, with no undesired pairings observed. Bispecific IgE antibodies also showed a dose-dependent binding to their target antigens, and cell bridging experiments demonstrated simultaneous binding of two different antigens. As antibodies mediate a major part of their effector functions through interaction with Fc receptors (FcRs) expressed on immune cells, we confirmed FcεR binding by inducing in vitro mast cell degranulation and demonstrating in vitro and in vivo monocyte-mediated cytotoxicity against target antigen-expressing Chinese hamster ovary cells. Moreover, we demonstrated that the IgE bsAb construct was significantly more efficient in mediating antibody-dependent cell toxicity than its IgG1 counterpart. In conclusion, we describe the successful development of first bispecific IgE antibodies with superior antibody-dependent cell toxicity-mediated cell killing in comparison to IgG bispecific antibodies. These findings highlight the relevance of IgE-based bispecific antibodies for clinical application.

Basophil-derived amphiregulin is essential for UVB irradiation-induced immune suppression.

UVB irradiation (290-320 nm) is used to treat skin diseases like psoriasis and atopic dermatitis, and is known to suppress contact hypersensitivity (CHS) reactions in mouse models. Regulatory T cells (Treg cells) have been shown to be responsible for this UVB-induced suppression of CHS. The epidermal growth factor (EGF)-like growth factor amphiregulin (AREG) engages EGFR on Treg cells and, in different disease models, it was shown that mast cell-derived AREG is essential for optimal Treg cell function in vivo. Here we determined whether AREG has a role in UVB-induced, Treg cell-mediated suppression of CHS reactions in the skin. Our data show that AREG is essential for UVB-induced CHS suppression. In contrast to the general assumption, however, mast cells were dispensable for UVB-induced immune suppression, whereas basophil-derived AREG was essential. These data reveal, to our knowledge, a previously unreported function for basophils in the homeostasis of immune responses in the skin. Basophils thus fulfill a dual function: they contribute to the initiation of effective type 2 immune responses and, by enhancing the suppressive capacity of local Treg cell populations, also to local immune regulation in the skin.

Murine model for non-IgE-mediated asthma.

There is increasing evidence that inflammatory mechanisms other than atopy or eosinophilic inflammation may be involved in the pathogenesis of asthma. The mechanisms associated with non-atopic (non-IgE) or neutrophil-mediated asthma are poorly investigated. Non-atopic airway inflammation and hyperresponsiveness was induced in mice by skin sensitization with dinitrofluorobenzene (DNFB) followed by intra-airway challenge with dinitrobenzene sulfonic acid (DNS). Acute bronchoconstriction and mast cell activation were observed shortly after challenge. Increased levels of the major mast cell mediator, TNF-alpha, were found in the bronchoalveolar lavage fluid of DNFB-sensitized. Mast cells play a key role in the early release of TNF-alpha since mast-cell-deficient WBB6F1-W/Wv mice did not show an increase in TNF-alpha release after DNFB-sensitization and DNS challenge compared to their ++ littermates. Features of the late-phase pulmonary reaction included mononuclear and neutrophilic cell infiltration, pulmonary edema, in vitro tracheal hyperreactivity and in vivo airway hyperresponsiveness. These characteristics bear marked similarity with those observed in non-atopic asthmatic patients. Therefore, this model can be used to further study the mechanisms potentially responsible for the development of non-IgE-mediated asthma.

The tachykinin NK1 receptor is crucial for the development of non-atopic airway inflammation and hyperresponsiveness.

Mast cell activation, bronchoconstriction, inflammation and airway hyperreactivity are prominent features of non-atopic hypersensitivity reactions in mouse airways. We studied the role of tachykinin receptors in mice that were skin-sensitized with dinitrofluorobenzene (or vehicle) and challenged intranasally with dinitrobenzene sulfonic acid. Tachykinin NK1 receptor blockade, by treatment with the antagonist RP67580, or absence of the tachykinin NK1 receptor resulted in a strong reduction in the accumulation of neutrophils in the bronchoalveolar lavage fluid, and in the development of tracheal hyperreactivity in mice 48 h after challenge. In contrast, treatment with the tachykinin NK2 receptor antagonist SR48968 did not affect the dinitrofluorobenzene-induced hypersensitivity reaction. We have previously shown that mast cells play a crucial role in the development of non-atopic asthma. However, we did not observe an inhibitory effect of the tachykinin receptor antagonists or the genetic absence of tachykinin NK1 receptors on mast cell protease release. In conclusion, distal from mast cell activation, the tachykinin NK1 receptor is crucial for the infiltration of pulmonary neutrophils and the development of tracheal hyperreactivity in non-atopic asthma.

Functional expression of neurokinin 1 receptors on mast cells induced by IL-4 and stem cell factor.

It is widely accepted that neurokinin 1 (NK(1)) receptors are not generally expressed on mast cells but little is known about their expression in inflammation. The present study shows expression of NK(1) receptors on bone marrow-derived mast cells (BMMC) under the influence of IL-4 or stem cell factor (SCF). Highest expression was found when both cytokines are present. Six days of coculture with the cytokines IL-4 and SCF showed significant expression of NK(1) receptors (NK(1) receptor(+)/c-kit(+) BMMC; control: 7%, IL-4/SCF: 16%), while 12 days of cytokine coculture increased this expression to 37% positive cells. A longer coculture with IL-4 and SCF did not give an additional effect. Increased expression in IL-4/SCF-treated BMMC was further confirmed using Western blot analysis. Next, we demonstrated the functional relevance of NK(1) receptor expression for mast cell activation, resulting in an enhanced degranulation upon stimulation by substance P. BMMC activation was significantly diminished by the NK(1) receptor antagonist RP67580 (10 micro M) when stimulated with low concentrations of substance P. The inactive enantiomer RP65681 had no effect. In addition, BMMC cultured from bone marrow of NK(1) receptor knockout mice showed significantly decreased exocytosis to low concentrations of substance P. The present study clearly shows that NK(1) receptor-induced activation contributes significantly at low physiological substance P concentrations (<100 micro M). In conclusion, BMMC were shown to express NK(1) receptors upon IL-4/SCF coculture. This expression of NK(1) receptors has been demonstrated to be of functional relevance and leads to an increase in the sensitivity of BMMC to substance P.

Key role for mast cells in nonatopic asthma.

The mechanisms involved in nonatopic asthma are poorly defined. In particular, the importance of mast cells in the development of nonatopic asthma is not clear. In the mouse, pulmonary hypersensitivity reactions induced by skin sensitization with the low-m.w. compound dinitrofluorobenzene (DNFB) followed by an intra-airway application of the hapten have been featured as a model for nonatopic asthma. In present study, we used this model to examine the role of mast cells in the pathogenesis of nonatopic asthma. First, the effect of DNFB sensitization and intra-airway challenge with dinitrobenzene sulfonic acid (DNS) on mast cell activation was monitored during the early phase of the response in BALB/c mice. Second, mast cell-deficient W/W(v) and Sl/Sl(d) mice and their respective normal (+/+) littermate mice and mast cell-reconstituted W/W(v) mice (bone marrow-derived mast cells-->W/W(v)) were used. Early phase mast cell activation was found, which was maximal 30 min after DNS challenge in DNFB-sensitized BALB/c, +/+ mice but not in mast cell-deficient mice. An acute bronchoconstriction and increase in vascular permeability accompanied the early phase mast cell activation. BALB/c, +/+ and bone marrow-derived mast cell-->W/W(v) mice sensitized with DNFB and DNS-challenged exhibited tracheal hyperreactivity 24 and 48 h after the challenge when compared with vehicle-treated mice. Mucosal exudation and infiltration of neutrophils in bronchoalveolar lavage fluid associated the late phase response. Both mast cell-deficient strains failed to show any features of this hypersensitivity response. Our findings show that mast cells play a key role in the regulation of pulmonary hypersensitivity responses in this murine model for nonatopic asthma.

Mast cell-derived TNF-alpha primes sensory nerve endings in a pulmonary hypersensitivity reaction.

TNF-alpha is a cytokine associated with inflammatory diseases, including asthma. Increased levels of TNF-alpha were found in the bronchoalveolar lavage fluid of mice undergoing a dinitrofluorobenzene (DNFB)-induced non-IgE-mediated pulmonary hypersensitivity reaction. We report in this work that TNF-alpha increases the susceptibility of sensory neurons to dinitrobenzene sulfonic acid (DNS) and capsaicin, leading to a tracheal vascular hyperpermeability response in DNFB-sensitized and DNS-challenged mice. mAb against TNF-alpha or the TNFR1 inhibited this hyperpermeability response in DNFB-sensitized and DNS-challenged mice. Furthermore, the hyperpermeability response after DNS challenge was abolished in DNFB-sensitized mast cell-deficient WBB6F(1)-W/W(V) mice. These animals showed a remarked decrease of TNF-alpha bronchoalveolar lavage fluid levels after a single DNS challenge. The hyperpermeability response after DNS challenge was regained in mast cell-deficient mice after mast cell reconstitution. These findings indicate a prominent role for TNF-alpha and its TNFR1 in the DNFB-induced tracheal hyperpermeability response. We propose that a priming effect of mast cell-derived TNF-alpha on the sensory neurons could be the mechanism of action of TNF-alpha in the vascular hyperpermeability response in tracheas of mice undergoing a pulmonary hypersensitivity reaction.

Characterization of a phosphorylated peptide and peptoid and peptoid-peptide hybrids by mass spectrometry.

Nano-electrospray tandem mass spectrometry (nano-ES-MS/MS) was used to record collision-induced dissociation (CID) spectra of a set of peptoid-peptide hybrids and the complete peptoid derived from the phosphopeptide Ac-pTyr-Glu-Thr-Leu-NH(2) (1). The presence of B and Y''-type fragment ions in the tandem mass spectra of the protonated molecular ions [M + H](+) allowed confirmation of sequence similar to mass spectrometric sequence analysis in peptides. In the isomeric peptoid compounds studied, one or several amino acid residues were replaced by peptoid residues (N-substituted glycine residues), which resulted in characteristic tandem mass spectra with differently increased relative abundances of Y''-and B-type fragment ions. The increment of a particular Y''-ion was directly correlated to the position of a peptoid residue present. In addition to these increased peak intensities, other characteristic peaks were also observed compared with the spectrum of reference peptide 1. When a peptoid phosphotyrosine was incorporated, the presence of this residue was apparent from the occurrence of a relatively intense peak at m/z 187 representing the positively charged side-chain of phosphotyrosine, which was almost absent in the spectrum of the reference peptide 1. Since the threonine side-chain had to be translated into the homo peptoid analog this substitution was apparent from the presence of [M + H](+) and fragment ions 14 mass units higher than observed in the spectrum of the reference phosphopeptide 1. The presence of an NLeu peptoid residue could be confirmed by the specific fragmentation of the immonium ion showing an intense peak in its tandem mass spectrum at m/z 57, which results from the loss of an neutral imine molecule leading to a positively charged [C(4)H(9)](+) ion. By means of these mass spectrometric characteristics, all isomeric peptoid compounds could be distinguished from each other and characterized. The methods used appear to be very useful in future studies of peptoids and peptoid-peptide hybrids.