The third molecule associated with interleukin 2 receptor alpha and beta chain.

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• The high-affinity Interleukin 2 (IL-2) receptor is crucial for T cell function.
• Affinity cross-linking studies reveal alpha (Tac) and beta chains involved in IL-2 binding.

Purpose of the Study:

• To investigate the composition of IL-2 binding complexes.
• To identify novel IL-2 binding proteins beyond the known alpha and beta chains.

Main Methods:

• Affinity cross-linking of Interleukin 2 (IL-2) to human T cells.
• Immunoprecipitation using anti-Tac and anti-beta chain antibodies.
• Analysis of protein bands via SDS-PAGE.

Main Results:

• Identified triplet bands in IL-2 receptor cross-linking: 70 kDa alpha chain-IL-2 and a 90/80 kDa doublet.
• Observed cell lines expressing alpha and beta chains but lacking the lower 80 kDa doublet band.
• Immunoprecipitation with anti-beta chain antibody detected the upper 90 kDa band but not the lower 80 kDa band.

Conclusions:

• The lower 80 kDa band represents an unknown IL-2 binding protein (p65), distinct from the beta chain.
• This novel protein (p65) likely participates with the beta chain in intermediate-affinity IL-2 binding.
• Further research is warranted to elucidate the precise role of p65 in IL-2 receptor signaling.