We report the isolation and characterization of 19 classes of nonrearranging T cell-specific cDNA clones and two cDNA clones encoding the a and /3 chains of the T-cell antigen receptor from a human T-cell line, Jurkat. Results indicate that the human a-chain gene, like its /8-chain counterpart, undergoes somatic rearrangement in T cells. In addition, it shows sequence homology to its P-chain counterpart and immunoglobulin, indicating that the human a chain is also a member of the immunoglobulin supergene family. Sequence comparison suggests that the a chain also may be composed of variable (V), diversity (D), joining (J), and constant (C) region gene segments. The protein deduced from the cDNA sequence has a molecular weight of 29,995 and possesses six potential N-glycosylation sites. The availability of a-and /3-chain genes of the T-cell receptor from the same T-cell line provides tools to study their possible roles in recognition of antigens and major histocompatibility complex products by the human T-cell receptor.Antigen recognition by T lymphocytes is mediated by the T-cell antigen receptor composed of an a-and /3-chain heterodimer situated on the surface of these immunocompetent cells (1-3). About a year ago, we (4) and Hedrick et al.(5) cloned cDNAs that specified, respectively, the /3 chain of the human and mouse T-cell receptor (6). Subsequent studies have indicated that the genes encoding these structures undergo somatic rearrangement in T lymphocytes (7) and are homologous to the Ig genes (8). In addition, their genomic structures are similar, but not identical in organization, to Ig genes (9-13). These results indicate that genes encoding the T-cell receptor, at least the /8-chain gene, are different from Ig genes, though they most likely share a common ancestor (8). The finding that the human /3-chain variable (V) and constant (C) region genes (V and C) are located on chromosome 7 (14), where there are no Ig genes, confirmed that these genes are independent of Ig genes. These observations, coupled with the fact that a and ,B chains are approximately the same size, suggest that the a chain is probably also Ig-related and may contain similar V and C domains (8).In this manuscript, we report the analysis of a number of human T-cell-specific cDNA clones and describe the characterization and sequence of a human T-cell clone with homology to the a chain ofthe human T-cell antigen receptor. The results reveal that, like the /B-chain genes of the T-cell receptor (4, 5), the a-chain genes are homologous to Ig genes and undergo somatic rearrangement in T cells. While these studies were in progress, isolation of the murine a-chain cDNA (15, 16) and partial protein sequence of the human a chain (17, 18) were reported. The elucidation of the a and 83 chains of the T-cell receptor should provide the molecular tools necessary for the study of the recognition of antigens and major histocompatibility complex products by human T cells.

SSR programs can benefit elderly patients at risk for institutionalization after acute hospitalization by improving their functioning and mobility, and allowing them to return to the community.

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Traditional perceptions that view leadership as a top-down process are increasingly challenged by so-called critical perspectives that acknowledge that leadership may involve several people. This article explores a particular type of these other leadership constellations, namely co-leadership where members share several leadership responsibilities.Drawing on more than twenty hours of authentic discourse data recorded in two workplaces in Hong Kong, we employ the analytical concepts of face and identity to identify and describe some of the complex processes through which co-leadership is enacted. Our particular focus is situations in which members of the co-leadership team disagree with each other.Our findings indicate that co-leadership is a dynamic process in which both members position themselves and each other as leader and co-leader at different moments throughout an interaction. This dynamic nature can be captured particularly well by exploring how face-work and identity construction are accomplished in interlocutors' everyday workplace talk. (Co-leadership, identity, face, workplace discourse, Hong Kong)*

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