https://www.sciencedirect.com/science/article/abs/pii/S0091674924003324
Journal of Allergy and Clinical Immunology Available online 7 April 2024
Suzanne M. Barshow, Maidul Islam, Scott Commins, Matthew S. Macauley, James C. Paulson, Michael D. Kulis
Key Messages:
• In vitro incubation of human basophils with monoclonal anti-IgE directly conjugated to CD33 ligand (anti-IgE-CD33L) significantly reduces basophil degranulation upon both antigen-specific (peanut) and antigen-non-specific (polyclonal anti-IgE) stimulation.
• This suppression of basophil degranulation is specific to signaling mediated through the IgE-FcεRI complex and is markedly enhanced when incubated with anti-IgE-CD33L overnight compared to 1 hour.
• Anti-IgE-CD33L’s ability to suppress IgE-mediated basophil degranulation to subsequent antigen exposure could have broad implications for the treatment of food, drug, and environmental allergies.
Abstract
Background
Siglec-3 (CD33) is a major Siglec expressed on human mast cells and basophils and engagement of CD33 leads to inhibition of cellular signaling via immunoreceptor tyrosine-based inhibitory motifs (ITIMs).
Objective
We sought to inhibit human basophil degranulation by simultaneously recruiting inhibitory CD33 to the IgE-FcεRI complex using monoclonal anti-IgE directly conjugated to CD33 ligand (CD33L).
Methods
Direct and indirect basophil activation tests (BAT) were used to assess both antigen-specific (peanut) and antigen non-specific (polyclonal anti-IgE) stimulation. Whole blood from allergic donors was used for direct BAT, whereas non-food allergic donor blood was passively sensitized with peanut-allergic plasma in the indirect BAT. Blood was incubated with anti-IgE-CD33L or controls for one hour or overnight, then stimulated with peanut, polyclonal anti-IgE, or N-formylmethionyl-leucyl-phenylalanine (fMLP) for 30 minutes. Degranulation was determined by measuring CD63 expression on the basophil surface by flow cytometry.
Results
Incubation for one hour with anti-IgE-CD33L significantly reduced basophil degranulation after both allergen-induced (peanut) and polyclonal anti-IgE stimulation, with further suppression after overnight incubation with anti-IgE-CD33L. As expected, anti-IgE-CD33L did not block basophil degranulation due to fMLP, providing evidence that this inhibition is IgE-pathway specific. Finally, CD33L is necessary for this suppression, as monoclonal anti-IgE without CD33L was unable to reduce basophil degranulation.
Conclusions
Pre-treating human basophils with anti-IgE-CD33L significantly suppressed basophil degranulation through the IgE-FcεRI complex. The ability to abrogate IgE-mediated basophil degranulation is of particular interest, as treatment with anti-IgE-CD33L prior to antigen exposure could have broad implications for the treatment of food, drug, and environmental allergies.
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