Differential binding of IL-1 alpha and IL-1 beta to receptors on B and T cells.
The interleukin 1 receptors (IL-1R) on the human B lymphoma RAJI and on the murine thymoma EL4-6.1 have been characterized. Equilibrium binding analysis using both 125I-labeled IL-1 alpha and IL-1 beta showed that RAJI cells have a higher number of binding sites/cell for IL-1 beta (2400, Kd 2.2 nM) than for IL-1 alpha (316, Kd 0.13 nM). On the other hand, EL4-6.1 cells have more receptors/cell for IL-1 alpha (22 656, Kd 1 nM) than for IL-1 beta (2988, Kd 0.36 nM). Dexamethasone (DXM) induced on RAJI cells a time-dependent increase in binding sites for both IL-1 beta and IL-1 alpha without affecting their binding affinities. However, while receptor-bound 125I-IL-1 alpha was displaced with equal efficiency by both IL-1 forms, only unlabeled IL-1 beta could effectively displace 125I-IL-1 beta. Cross-linking experiments indicated that RAJI cells have a predominant IL-1R of about 68 kDa, while EL4-6.1 cells have an IL-1-binding polypeptide of 80 kDa. These results suggest that B and T cells possess structurally different IL-1R with distinct binding properties for IL-1 alpha and IL-1 beta.
Scapigliati
G
G
Laboratory of Immunopharmacology, Sclavo Research Centre, Siena, Italy.
Ghiara
P
P
Bartalini
M
M
Tagliabue
A
A
Boraschi
D
D
D000818:Animals; D001345:Autoradiography; D001402:B-Lymphocytes / Q000378:metabolism*; D001667:Binding, Competitive; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D017472:Receptors, Interleukin-1; D013601:T-Lymphocytes / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D003432:Cross-Linking Reagents; D007375:Interleukin-1; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1