Complexes of allergen and specific IgG antibodies activate human neutrophils

Aim To investigate whether AICs activate neutrophils via Fc γ R and influence allergen-uptake and presentation Methods Major birch pollen allergen was incubated with different monoclonal antibodies (mAbs) and their effector-attenuated LALA-variants. AIC formation was analysed by dynamic light scattering. Neutrophils isolated from birch pollen allergic and non-allergic donors were stimulated with GM-CSF and IFN- γ . Fc γ R expression and internalisation of fluorescence-labelled allergen were determined by flow cytometry. Neutrophils pulsed with allergen, AICs or LALA-AICs were subjected to DNA-release assays and served as APC for autologous allergen-specific T-cells. Results Cytokine-primed neutrophils showed upregulated Fc γ RI/CD64, downregulated Fc γ RIII/CD16, and unaltered Fc γ RII/CD32 expression. AICs with one and two mAbs were generated. Neutrophils phagocytosed larger AICs and LALA-AICs more effectively than smaller complexes and non-complexed allergen. Compared to non-complexed allergen, T-cell proliferation was inconclusive when neutrophils were pulsed with AICs and enhanced when pulsed with LALA-AICs. AICs but not LALA-AICs induced NET-release. Conclusion Fc γ R-independent phagocytosis of AICs enhanced the allergen-presenting activity of neutrophils but Fc γ R-mediated NET induction might interfere with the T cell stimulatory properties. Our results suggest a novel link between humoral and cellular responses to allergens.