title: Binding and internalization of interleukin 1 by T cells. Direct evidence for high- and low-affinity classes of interleukin 1 receptor.
abstract: In this report we describe, on the basis of direct IL-1 binding assays and IL-1 internalization studies, the existence of two classes of IL-1-R on a variety of T cell types. Cells of the EL4-6.1 thymoma express large numbers (approximately 20,000 per cell) of IL-1-R that have a Kd of approximately 300 pM for IL-1. Even though these receptors make up 98-99% of the total IL-1-R per cell, they appear to be nonfunctional, based on their inability to endocytose IL-1. A minor class of IL-1-R (200-400/cell) has an approximately 100-fold higher affinity for IL-1 (Kd, approximately 5 pM) and can rapidly internalize the ligand upon binding. All of the biological activity of IL-1 can be shown to occur via binding to high-affinity IL-1-R since the IL-1 concentration giving half-maximum biological activity in EL4-6.1 cells corresponds precisely to the Kd of this class of receptor. Other cell types, including normal T cells, also express both high- and low-affinity IL-1-R, but the absolute number of receptors per cell is considerably less.
mesh_terms: D002460:Cell Line; D007375:Interleukin-1 / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007700:Kinetics; D011971:Receptors, Immunologic / Q000032:analysis*; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000032:analysis / Q000378:metabolism*
chemical_list: D007375:Interleukin-1; D007457:Iodine Radioisotopes; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins