Similarity between the interleukin 1 receptors on a murine T-lymphoma cell line and on a murine fibroblast cell line.

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Abstract
Interleukin 1.beta. (IL-1.beta.), one of two different polypeptide hormones with interleukin 1 (IL-1) biological activity, produced by activated human monocytes, is a 17.5-kDa protein. IL-1.beta. binds specifically to a variety of cells; the cellular distribution of binding is consistent with reported biological responsiveness. In this report we show that two unrelated, but IL-1-responsive, cell lines, LBRM-33-1A5, a T-lymphoma line, and BALB/3T3, a fibroblast line, bind 125I-labeled IL-1.beta. via similar plasma membrane receptor molecules. The T-lymphoma cells possess 238 .+-. 16 plasma membrane receptors per cell and bind 125I-labelled IL-1.beta. with an affinity of 3.6 .+-. 0.9 .times. 109 M-1. The IL-1 receptor has a molecular size of .apprxeq. 79.5 kDa, as estimated by affinity cross-linking. The fibroblasts possess 4.8 .+-. 0.5 .times. 103 IL-1 receptors per cell and bind 125I-labeled IL-1.beta. with an affinity of 2.6 .+-. 0.5 .times. 109 M-1. The molecular size of the receptor molecule on the fibroblasts is .apprxeq. 78 kDa. Despite the similarity in the characteristic of the ligand-receptor system on the two different cell types, the biological responses of the two cell types to IL-1.beta. occur at IL-1.beta. concentrations that differ by four orders of magnitude.