Neutralizing monoclonal antibodies can potentiate IL-5 signaling

Area of Science:

• Immunology
• Cell Biology

Background:

• Interleukin-5 (IL-5) is crucial for eosinophil survival, differentiation, and function.
• IL-5 signals through a receptor (IL-5R) composed of alpha and beta chains, shared with IL-3 and GM-CSF receptors.

Purpose of the Study:

• To characterize the epitopes of three monoclonal antibodies (mAbs) against IL-5: 5A5, 1E1, and H30.
• To investigate the functional effects of these mAbs on IL-5 signaling and eosinophil proliferation.

Main Methods:

• Epitope mapping of anti-IL-5 mAbs.
• Assays measuring eosinophil proliferation in response to human IL-5 (hIL-5) and mAbs.
• Analysis of JAK-2 dependency and IL-5Ralpha chain expression.

Main Results:

• Two mAbs, 5A5 and H30, enhanced hIL-5-induced proliferation in a JAK-2-dependent manner.
• This potentiation occurred at sub-optimal hIL-5 concentrations and required mAb-mediated cross-linking of IL-5R complexes.
• The effect was observed only on cell lines expressing a hybrid human/mouse IL-5Ralpha chain.

Conclusions:

• Certain anti-IL-5 mAbs can unexpectedly potentiate IL-5 signaling and eosinophil proliferation.
• These findings have implications for the clinical use of humanized anti-IL-5 mAbs, necessitating evaluation for unintended potentiating effects.
• Understanding IL-5R stoichiometry and topology is critical for interpreting mAb activity.