Monoclonal antibodies targeting ST2L Domain 1 or Domain 3 differentially modulate IL-33-induced cytokine release by human mast cell and basophilic cell lines

•Monoclonal antibodies targeting Domain 1 or Domain3 of the IL-33 receptor ST2L differentially affect signaling complex formation.•The anti-ST2L antibodies differentially affect gene expression and cytokine release by mast cells as compared to basophils.•Blocking the first step in the formation of the ST2L signaling complex with an anti-ST2L Domain 1 mAb resulted in complete inhibition.•Partial inhibition of the pathway as well as aberrant signaling was observed in mast cells treated with an anti-ST2L Domain 3 mAb. The cell-surface receptor ST2L triggers cytokine release by immune cells upon exposure to its ligand IL-33. To study the effect of ST2L-dependent signaling in different cell types, we generated antagonist antibodies that bind different receptor domains. We sought to characterize their activities in vitro using both transfected cells as well as basophil and mast cell lines that endogenously express the ST2L receptor. We found that antibodies binding Domain 1 versus Domain 3 of ST2L differentially impacted IL-33-induced cytokine release by mast cells but not the basophilic cell line. Analysis of gene expression in each cell type in the presence and absence of the Domain 1 and Domain 3 mAbs revealed distinct signaling pathways triggered in response to IL-33 as well as to each anti-ST2L antibody. We concluded that perturbing the ST2L/IL-33/IL-1RAcP complex using antibodies directed to different domains of ST2L have a cell-type-specific impact on cytokine release, and may indicate the association of additional receptors to the ST2L/IL-33/IL-1RAcP complex in mast cells.