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Two high-affinity interleukin 1 receptors represent separate gene products
R Chizzonite1, T Truitt, P L Kilian
1Department of Molecular Genetics, Roche Research Center, Hoffmann-La Roche Inc., Nutley, NJ 07110.
Summary
Two distinct Interleukin 1 (IL-1) receptors exist. One IL-1 receptor is found on T cells, fibroblasts, and epithelial cells, while a different IL-1 receptor is present on immune cells like macrophages and B cells.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Interleukin 1 (IL-1) is a crucial polypeptide hormone involved in diverse biological activities.
- IL-1 interacts with specific surface receptors on various cell types, mediating its effects.
- Previous studies suggested heterogeneity in IL-1 receptor binding affinities across different cell populations.
Purpose of the Study:
- To investigate the molecular basis for differential Interleukin 1 (IL-1) binding affinities observed in various cell types.
- To characterize the specific IL-1 receptor expressed on T cells, fibroblasts, and epithelial cells.
- To determine if the IL-1 receptor on immune cells (macrophages, B cells) is distinct from that on other cell types.
Main Methods:
- Equilibrium binding studies were performed using radiolabeled IL-1.
- Affinity cross-linking experiments were conducted to identify receptor protein sizes.
- Monoclonal and polyclonal antibodies specific to the T cell IL-1 receptor were utilized.
- Immunoprecipitation assays were employed to isolate IL-1 receptor complexes.
- S1 nuclease protection assays were used to analyze IL-1 receptor mRNA expression.
Main Results:
- Equilibrium binding revealed higher affinity IL-1 receptors on T cells, fibroblasts, and epithelial cells compared to bone marrow cells, pre-B cells, and macrophages.
- Affinity cross-linking identified an approximately 100-kDa protein on T cells/fibroblasts and an 80-kDa protein on pre-B cells/macrophages.
- Specific antibodies blocked IL-1 binding to T cells, fibroblasts, and epithelial cells but not to immune cells.
- Antibodies immunoprecipitated the IL-1 receptor complex from T cells/fibroblasts, but not from immune cells.
- S1 nuclease protection assays confirmed identical IL-1 receptor mRNA in T cells/fibroblasts, but its absence in pre-B cells/macrophages.
Conclusions:
- Mouse T cells, fibroblasts, and epithelial cells express an identical Interleukin 1 (IL-1) receptor.
- The IL-1 receptor found on pre-B cells, macrophages, and bone marrow cells is encoded by a different gene.
- This study elucidates the molecular distinction between IL-1 receptors, explaining differential cellular responses to IL-1 signaling.