Characterization of two high affinity human interleukin-8 receptors

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Interleukin 8 (IL-8) and melanocyte growth-stimulatory activity/gro (MGSA) are proinflammatory cytokines.
• These cytokines attract and activate neutrophils.
• Two distinct IL-8 receptors, IL-8R-A and IL-8R-B, have been identified.

Purpose of the Study:

• To characterize the binding affinities of IL-8R-A and IL-8R-B for IL-8 and MGSA.
• To investigate the cellular responses mediated by these receptors.
• To determine the presence and role of these receptors in human neutrophils.

Main Methods:

• Expression of IL-8R-A and IL-8R-B in mammalian cells.
• Binding assays to determine receptor affinities for IL-8 and MGSA.
• Measurement of intracellular calcium (Ca2+) concentration changes upon ligand binding.
• Blot hybridization to detect receptor mRNA in human neutrophils.

Main Results:

• Both IL-8R-A and IL-8R-B bind IL-8 with high affinity (Kd ≈ 2 nM).
• IL-8R-A exhibits low affinity for MGSA (Kd ≈ 450 nM), while IL-8R-B binds MGSA with high affinity (Kd ≈ 2 nM).
• Ligand binding triggers a transient increase in intracellular Ca2+; IL-8R-A responds to IL-8, while IL-8R-B responds to both IL-8 and MGSA.
• mRNA for both receptors is present in human neutrophils, and their binding and signaling profiles explain neutrophil responses to IL-8 and MGSA.

Conclusions:

• The distinct binding properties of IL-8R-A and IL-8R-B for IL-8 and MGSA are characterized.
• The expression of both receptors in neutrophils accounts for their differential responses to these cytokines.
• This study elucidates the molecular basis for neutrophil chemoattraction and activation by IL-8 and MGSA.