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.

The role of self-peptides in positive selection of CD4+ T cells has been controversial. We show that some self-peptides are presented by the MHC class II molecule I-A(b) in mice lacking Ii or H-2M but not in mice expressing a transgene-encoded peptide fused to I-A(b). In experiments using specific antibodies to block selection, these low-abundance self-peptides were implicated in the positive selection of some CD4+ T cells in H-2M-/- mice. However, all three mutant backgrounds failed to positively select two class II-restricted transgenic T cell receptors. Our findings suggest that minor components of the self-peptide repertoire can contribute to positive selection of a significant number of CD4+ T cells. In addition, the data suggest that T cell receptor repertoires selected in wild-type mice and in mice displaying limited spectra of self-peptides are distinct.

SummaryInsulin-dependent diabetes mellitus (IDDM) is associated with autoreactivity against GAD but the diagnostic sensitivity (positivity in disease) and specificity (negativity in health) of isoform-specific GAD antibodies have yet to be defined in assay systems suitable for screening large number of samples. One set of IDDM patient (n = 10) and control (n = 50) standard sera were used to develop quantitative antibody assays with in vitro synthesized recombinant 35S-methionine-labelled GAD65 and GAD67, respectively, and protein A-Sepharose to separate free from antibody-bound ligand. Binding levels were not normally distributed (p < 0.0001) and therefore, the diagnostic accuracy of GAD antibodies was analysed by the ROC plots in population-based, consecutively-diagnosed, recent onset, 0-14year-old patients (n = 105), and matched, healthy control subjects (n = 157). The ROC plots showed that the diagnostic sensitivity of GAD65 antibodies was 77 % and the specificity 92 % compared with 8 % and 98 %, respectively for GAD67 antibodies. In the IDDM sera, GAD65 and GAD67 antibodies were concordant in 7% (6 of 81) and GAD65 antibodies and ICA in 89 % (72 of 81) without a correlation between the autoantibody levels. Autoantibodies to recombinant human islet GAD65 are specific and sensitive markers for childhood IDDM in this immunoassay with in vitro synthesized 35S-methioninelabelled recombinant GAD. [Diabetologia (1994) Abbreviations: IDDM, insulin-dependent diabetes mellitus; GAD, glutamic acid decarboxylase; ROC, receiver-operating characteristic; ICA, islet cell antibodies; JDF, Juvenile Diabetes Foundation 10p11.3-p12 [7]. GAD65 shows 65 % amino acid identity with GAD67, the isoform coded for by the GAD1 gene on chromosome 2q31 [7][8][9]. The molecular cloning of full-length human islet GAD65 [7] and rat islet GAD67 [10] cDNA has made it possible to demonstrate autoreactivity in diabetes to the recombinant proteins in both eukaryotic [11,12] and bacterial [13] expression systems. GAD65 (but not GAD67) is expressed in human islets [11,14], however, variable reactivity of patient sera has been reported [12,13,[15][16][17][18][19]. GAD65 specificity of IDDM sera was first demonstrated in our immunoprecipitation assay with recombinant GAD expressed in transfected cells [12] and recently confirmed in other assays with recombinant antigens [18,20]. The use of different assay systems and species-specific GAD65 and GAD67 may explain the lower frequency of GAD67 antibodies in these compared to previous reports [13,16]. We now report the