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Viertlboeck, B. C.; Habermann, Felix A.; Schmitt, R.; Groenen, M. A. M.; Du Pasquier, L.; Göbel, Thomas W. (2005): The chicken leukocyte receptor complex: A highly diverse multigene family encoding at least six structurally distinct receptor types. In: Journal of immunology, Vol. 175, No. 1: pp. 385-393
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The chicken Ig-like receptors (CHIR) have been described as two Igdomain molecules with long cytoplasmic tails containing inhibitory motifs. In this study, we demonstrate that CHIR form a large family, with multiple members showing great sequence variability among members as well as a great diversity in domain organization and properties of the transmembrane and cytoplasmic segments. We characterize various novel receptor types with motifs indicative of inhibitory, activating, or both functions. In addition to the inhibitory receptors with two ITIM, receptors with a single immunoreceptor tyrosine-based switch motif or receptors lacking a cytoplasmic domain were isolated. Activatingreceptors with a short cytoplasmic domain and a transmembrane arginine assembled with the newly identified chicken Fc is an element of RI gammachain. Three bifunctional receptor types were characterized composed of one or two C2-type Ig-like domains, a transmembrane region with apositively charged residue and combinations of cytoplasmic motifs suchas ITIM, immunoreceptor tyrosine-based switch motif, and YXXM. RT-PCRrevealed distinct expression patterns of individual CHIR. All receptor types shared a conserved genomic architecture, and in single Ig domain receptors a pseudoexon replaced the second Ig exon. Southern blot analyses with probes specific for the Ig1 domain were indicative of alarge multigene family. Of 103 sequences from the Ig1 domain of a single animal, 41 unique sequences were obtained that displayed extensive variability within restricted Ig regions. Fluorescence in situ hybridization localized the CHIR gene cluster to microchromosome 31 and identified this region as orthologous to the human leukocyte receptor complex.