Association of intercellular adhesion molecule 1 with the multichain high-affinity interleukin 2 receptor

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Previous studies demonstrated a physical interaction between a 95-kDa protein (p95) and the alpha subunit of the high-affinity interleukin 2 (IL-2) receptor.
• The 55-kDa alpha protein of the IL-2 receptor is crucial for high-affinity IL-2 binding and T-cell activation.

Purpose of the Study:

• To identify the 95-kDa protein (p95) interacting with the IL-2 receptor alpha subunit.
• To confirm the physical proximity and functional significance of the p95/ICAM-1 and IL-2 receptor interaction in T-cell responses.

Main Methods:

• Protein purification and amino acid sequencing to identify p95.
• Sequential immunoprecipitation using specific antibodies (OKT27, WEHI-CAM-1) to confirm protein identity.
• Cross-linking studies with radiolabeled IL-2 to assess proximity to the IL-2 receptor alpha subunit.
• Functional assays measuring T-cell proliferation in response to various stimuli in the presence of blocking antibodies.

Main Results:

• The 95-kDa protein (p95) was identified as human intercellular adhesion molecule 1 (ICAM-1).
• ICAM-1 was confirmed to be in close physical proximity to the IL-2 receptor alpha subunit on activated T cells.
• Antibodies against ICAM-1 (OKT27, OKT27b) inhibited T-cell proliferation in response to OKT3, soluble antigen, and mixed lymphocyte reactions, but not IL-2-induced proliferation.
• These findings suggest ICAM-1 is physically associated with the high-affinity IL-2 receptor.

Conclusions:

• ICAM-1 physically interacts with the high-affinity IL-2 receptor alpha subunit.
• This association may enhance T-cell activation by promoting homotypic T-cell interactions and focusing IL-2 signaling.
• The interaction could play a role in lymphocyte function-associated antigen 1 (LFA-1)/ICAM-1-mediated T-cell activation and IL-2 receptor function.