Interleukin-2 acutely induces protein leakage from the microcirculation

Area of Science:

• Immunology
• Oncology
• Microcirculation Physiology

Background:

• Interleukin-2 (IL-2) demonstrates efficacy in metastatic cancer regression.
• Therapeutic use of IL-2 is restricted by dose-dependent toxicities, notably vascular leak syndrome (VLS).
• Understanding the early microvascular mechanisms of IL-2-induced VLS is crucial for mitigating toxicity.

Purpose of the Study:

• To investigate the direct microvascular effects of IL-2.
• To quantify the earliest changes in microvascular permeability induced by IL-2.
• To elucidate the pathophysiology of IL-2-mediated vascular leak syndrome.

Main Methods:

• Utilized intravital microscopy for direct observation of microvascular effects in rat cremaster muscle.
• Employed fluorescein isothiocyanate-labeled albumin to assess macromolecular leakage in vivo.
• Administered IL-2 both intravenously and topically to differentiate systemic versus local effects.

Main Results:

• Both intravenous and topical IL-2 administration acutely induced macromolecular leakage from the microcirculation.
• Topical IL-2 application caused leakage without altering central hemodynamic parameters.
• No significant changes in arteriolar/venular diameter or blood flow were observed with topical IL-2, indicating leakage is independent of hemodynamic shifts.

Conclusions:

• IL-2 directly increases endothelial permeability, leading to macromolecular leakage.
• The observed vascular leak syndrome is primarily due to increased endothelial porosity.
• These findings suggest that IL-2's toxicity is a direct effect on microvascular endothelium, not mediated by hemodynamic changes.