Interleukin 2 and interleukin 15 (IL2 and IL15, respectively) provide quite distinct contributions to T-cell-mediated immunity, despite having similar receptor composition and signaling machinery. As most of the proposed mechanisms underlying this apparent paradox attribute key significance to the individual α-chains of IL2 and IL15 receptors, we investigated the spatial organization of the receptors IL2Rα and IL15Rα at the nanometer scale expressed on a human CD4+ leukemia T cell line using single-molecule-sensitive near-field scanning optical microscopy (NSOM). In agreement with previous findings, we here confirm clustering of IL2Rα and IL15Rα at the submicron scale. In addition to clustering, our single-molecule data reveal that a non-negligible percentage of the receptors are organized as monomers. Only a minor fraction of EL2Rα molecules reside outside the clustered domains, whereas ∼30% of IL15Rα molecules organize as monomers or small clusters, excluded from the main domain regions. Interestingly, we also found that the packing densities per unit area of both IL2Rα and IL15Rα domains remained constant, suggesting a 'building block' type of assembly involving repeated structures and composition. Finaltly, dual-color NSOM demonstrated co-clustering of the two α-chains. Our results should aid understanding the action of the EL2R-IL15R system in T cell fanction and also might contribute to the more rationale design of IL2R- or IL15R- %rgeted immunotherapy agents for treating human leukemia.
- Interleukin receptors IL2R
- Nanometer-scale membrane organization
- Near-field scanning optical microscopy (NSOM)
- Single-molecule detection
ASJC Scopus subject areas
- Cell Biology