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Repertoire Selection (repertoire + selection)
Selected AbstractsRepertoire selection by pre-B-cell receptors and B-cell receptors, and genetic control of B-cell development from immature to mature B cellsIMMUNOLOGICAL REVIEWS, Issue 1 2000Fritz Melchers Summary: During B-cell development the surrogate light (SL) chain is selectively expressed in progenitor and precursor B cells during the developmental stages of DH to JH and VH to DH JH rearrangements. Approximately half of all H chains produced by these rearrangements cannot pair with SL chains and cannot form a pre-B-cell receptor (pre-BCR). A spectrum of affinities between VpreB and individual VH domains generates preB cells with pre-BCR of different fitness which, in turn, determines the extent of the pre-B II-cell proliferation and the fidelity of allelic exclusion of the H chain locus. Once pre-BCR is expressed, SL chain expression is turned off. As pre-B II cells proliferate, SL is diluted out, thus limiting pre-BCR formation. As a consequence, pre-B II cells stop proliferating, become small and resting and begin to rearrange the L chain loci. Multiple rearrangements of the k L chain alleles are often detected in wild-type small pre-B II cells. Around 20% of the H chain-expressing small pre-B II cells also express L chains but do not display the Ig on the surface. Hence, it is likely that not all L chains originally generated in resting pre-B II cells can pair with the H chain previously present in that cell. The best fitting ones are selected preferentially to generate sIg+ B cells. Furthermore, the transition of immature B cells from the bone marrow to spleen and their development to mature cells appear as two separate steps controlled by different genes. [source] A phenotypically distinct subset of immature B cells exhibits partial activation, increased survival, and preferential expression of VhS107EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2003Emily Abstract We have observed that immature B cells (IgMlowIgD,) in the bone marrow of adult BALB/c mice exhibit heterogeneity, with a distinct subpopulation (,4,10%) expressing the CD43/S7 surface protein. These CD43/S7+ immature B cells often express other surface antigens associated with B cell activation (CD5, CD11b, PD-1). Generation of optimal numbers of CD43/S7+ immature B cells requires expression of a functional Btk protein, consistent with activation as a requisite for the CD43/S7+ immature B cell phenotype. Like typical CD43/S7, immature B cells, the CD43/S7+ immature B cells are predominantly resting cells, which are derived from cycling bone marrow B cell precursors. The CD43/S7+ immature B cell population exhibits enhanced survival in vivo upon administration of the apoptosis-inducing corticosteroid, dexamethasone. Finally, CD43/S7+ immature B cells show a fourfold increase in incidence of VhS107 , heavy chain expression compared to the CD43/S7, immature B cells. Therefore, in adult murine bone marrow, the presence of a phenotypically distinct immature B cellpopulation can be demonstrated which has undergone partial activation leading to increased survival and BCR-dependent Vh repertoire selection. [source] Visualizing thymocyte motility using 2-photon microscopyIMMUNOLOGICAL REVIEWS, Issue 1 2003Ellen A. Robey Summary:, Our view of a thymocyte based on its behavior in tissue culture and appearance in fixed tissue sections was of a round sessile cell. Its travel through the thymus might occur slowly, perhaps even passively, leaving it in contact with the support cells that happened to be in its immediate environment. However, when we got our first look at the behavior of thymocytes in a 3D cellular stromal cell environment, that picture changed dramatically. Instead we found that thymocytes are actively crawling, allowing them to explore their environment over relatively long distances and interact with peptide-major histocompatibility complex (pMHC)-bearing thymic stromal cells in both dynamic and stable modes. In this review, we discuss the implications of thymocyte motility for T-cell repertoire selection and for the mechanisms that determine the spatial organization of thymocyte subsets within the thymus. [source] Thymic development and repertoire selection: the rat perspectiveIMMUNOLOGICAL REVIEWS, Issue 1 2001Thomas Hünig Summary: This review summarizes our current knowledge of T-cell maturation and repertoire selection in the rat thymus. Some unique features of early thymocyte development and of CD4/CD8 lineage decision are described. A detailed analysis of lineage progression through the CD4, CD8 "double positive" compartment and T-cell receptor-induced CD8 T-cell maturation in cell culture is provided. A second emphasis is placed on interactions between germline-encoded T-cell receptor elements with MHC molecules in thymic repertoire selection and alloreactivity [source] B-cell antigen-receptor signalling in lymphocyte developmentIMMUNOLOGY, Issue 4 2003Leo D. Wang Summary Signalling through the B-cell antigen receptor (BCR) is required throughout B-cell development and peripheral maturation. Targeted disruption of BCR components or downstream effectors indicates that specific signalling mechanisms are preferentially required for central B-cell development, peripheral maturation and repertoire selection. Additionally, the avidity and the context in which antigen is encountered determine both cell fate and differentiation in the periphery. Although the signalling and receptor components required at each stage have been largely elucidated, the molecular mechanisms through which specific signalling are evoked at each stage are still obscure. In particular, it is not known how the pre-BCR initiates the signals required for normal development or how immature B cells regulate the signalling pathways that determine cell fate. In this review, we will summarize the recent studies that have defined the molecules required for B-cell development and maturation as well as the theories on how signals may be regulated at each stage. [source] | ||||||||||