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Beschreibung
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Ly 5 is a major cell surface component of T and B lymphocytes and most hematopoietic cells including promyelocytes, metamyelocytes, macrophages, eosinophils and neutrophils but is absent from mature erythroid cells (1). An interesting feature of the Ly 5 system is that members of this family of glycoproteins range in size from approximately 180 kDa to 240 kDa and differ in both protein sequence and carbohydrate content (2). Ly 5 alloantigens may be present in one of several molecular isoforms, and it has been postulated that each defines stages and lineages of hematopoietic differentiation (2). B lymphocytes express a 220 kDa form (B220) (3), while T lymphocytes indicate a more complicated pattern of expression with at least four forms identified by SDS-PAGE (2). Different patterns of expression have been identified between T lymphocyte subsets, indicating that expression of individual members is controlled in a cell-type specific fashion. Individual T cells may also express more than one member of the Ly 5 family and during activation, expression of the various forms may change (4). Additionally, there appears to be further Ly 5 modifications that occur as mature thymocytes migrate to peripheral lymphoid organs (4). Thus, the Ly 5 antigen exhibits inter and intratissue polymorphism, and it becomes clear that a programmed sequence of Ly 5 expression occurs during T cell differentiation and activation and that the forms expressed by lymphocyte populations are dynamic. anti-Ly 5.2 monoclonal antibody detects a 180 kDa isoform in thymus, spleen, and lymph node tissue as determined by SDS-PAGE. An additional antigen of 200 kDa was precipitated from splenic tissue and a very small amount of protein of approximately 180 kDa was precipitated from bone marrow tissue (5). The Ly 5.2 antigen has also been defined as a major component of "natural killer" cells and it has been further suggested that the Ly 5 (or "modified Ly 5") may be part of or close to a receptor on natural killer cells, for their target (6,7). Thus, this antibody in the presence of complement can be used to deplete/identify a cell population of Ly 5.2 bearing cells or used in the absence of complement to block natural killer activity.
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