Interleukin-1 alpha and -1 beta (IL-1 alpha and IL-1 beta) are cytokines that participate in the regulation of immune responses, inflammatory reactions, and hematopoiesis. A direct expression strategy was used to clone the receptor for IL-1 from mouse T cells. The product of the cloned complementary DNA binds both IL-1 alpha and IL-1 beta in a manner indistinguishable from that of the native T cell IL-1 receptor. The extracellular, IL-1 binding portion of the receptor is 319 amino acids in length and is composed of three immunoglobulin-like domains. The cytoplasmic portion of the receptor is 217 amino acids long.

cDNA clones corresponding to an Mr approximately 80,000 receptor (type I receptor) for interleukin‐1 (IL‐1) have been isolated previously by mammalian expression. Here, we report the use of an improved expression cloning method to isolate human and murine cDNA clones encoding a second type (Mr approximately 60,000) of IL‐1 receptor (type II receptor). The mature type II IL‐1 receptor consists of (i) a ligand binding portion comprised of three immunoglobulin‐like domains; (ii) a single transmembrane region; and (iii) a short cytoplasmic domain of 29 amino acids. This last contrasts with the approximately 215 amino acid cytoplasmic domain of the type I receptor, and suggests that the two IL‐1 receptors may interact with different signal transduction pathways. The type II receptor is expressed in a number of different tissues, including both B and T lymphocytes, and can be induced in several cell types by treatment with phorbol ester. Both IL‐1 receptors appear to be well conserved in evolution, and map to the same chromosomal location. Like the type I receptor, the human type II IL‐1 receptor can bind all three forms of IL‐1 (IL‐1 alpha, IL‐1 beta and IL‐1ra). Vaccinia virus contains an open reading frame bearing strong resemblance to the type II IL‐1 receptor.

Recent studies have demonstrated that DNA cleavage during V(D)J recombination is mediated by the RAG1 and RAG2 proteins. These proteins must therefore bind to the recombination signals, but the specific binding interaction has been difficult to study in vitro. Here, we use an in vivo one-hybrid DNA binding assay to demonstrate that RAG1, in the absence of RAG2, can mediate signal recognition via the nonamer, with the heptamer acting to enhance its binding. A region of RAG1 with sequence similarity to bacterial invertases is essential for DNA binding. Localization of RAG2 to the signal is dependent upon the presence of RAG1 and is substantially more efficient with a 12 bp spacer signal than with a 23 bp spacer signal.

Under most circumstances, allelic exclusion at the T cell receptor (TCR)beta locus is tightly regulated. Here, we describe a system in which TCRbeta allelic exclusion is overcome as a result of V(D)J recombination in peripheral CD4+ T cells. In TCRbeta chain transgenic mice, tolerogen-mediated chronic peripheral selection against cells expressing the transgene leads to surface expression of endogenous TCRbeta chains. Peripheral CD4+ T cells reexpress the recombination activating genes, RAG1 and RAG2, and contain signal end intermediates indicative of ongoing V(D)J recombination. The rescue from deletion of mature T cells expressing newly generated TCRbeta chains suggests that receptor revision plays a role in the maintenance of peripheral T cell tolerance.

ABSTRACTcDNA clones of the interleukin 1 (IL-1) receptor expressed in a human T-cell clone have been isolated by using a murine IL-1 receptor cDNA as a probe. The cytokines interleukins la and 1A3 (collectively IL-1) play a central role in mediating both immune responses and inflammatory reactions (for review, see refs. 1 and 2). IL-1 elicits its activities by binding to a specific receptor molecule on the surface of responsive cells (3). cDNA clones of the IL-1 receptor expressed in murine T cells have shown it to be a 557-amino acid transmembrane protein possessing a single membrane-spanning segment (4). The extracellular, ligandbinding portion of the molecule consists entirely of three immunoglobulin-like domains. The 217-amino acid intracellular portion, while large enough in principle to possess some enzymatic function, bears no compelling resemblance to any sequence currently in standard data bases. The cloned murine IL-1 receptor is capable, in transfection assays, of fully reconstituting both the ligand binding and the signal transduction properties of the native receptor. For example, when expressed transiently at very high levels in COS cells, the recombinant receptor possesses IL-1 binding characteristics that are indistinguishable from those of the natural receptor expressed in EL4 cells (4). Indeed, a secreted, soluble form of the IL-1 receptor, containing only the extracellular part of the molecule, binds IL-1 with an affinity identical to that of the receptor in EL4 cells, demonstrating that this is the only molecule involved in IL-1 binding in these cells (5). In addition, high-level stable expression of the recombinant receptor in Chinese hamster ovary (CHO) cells results in significantly enhanced sensitivity of these cells to IL-1 (6). The increase in sensitivity does not occur if the cytoplasmic domain of the receptor has been deleted and is most simply accounted for if all of the transfected receptors are functional in signaling. Thus, the recombinant murine IL-1 receptor is fully functional in signal transduction as well as in IL-1 binding.We have used the murine IL-1 receptor cDNA clone as a probe to isolate cDNA clones of the human IL-1 receptor from a human T-cell line and find the mouse and human receptors to be very similar molecules.t In addition, we have isolated a cDNA clone encoding the IL-1 receptor expressed in human dermal fibroblasts and have determined that its nucleotide sequence is identical to that of the IL-1 receptor expressed in human T cells. RESULTSWe have analyzed the IL-1 receptor expressed in a CD4+ CD8-human T-cell line (clone 22) (7). Resting clone 22 cells constitutively displayed two affinity classes of IL-1 receptor.