Robert M. J. Keehnen
University of Amsterdam
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Featured researches published by Robert M. J. Keehnen.
Current Topics in Microbiology and Immunology | 1999
Taher E.I. Taher; R. van der Voort; Lia Smit; Robert M. J. Keehnen; E. J. M. Schilder-Tol; Marcel Spaargaren; Steven T. Pals
Activation of naive B cells in the T cell areas of the secondary lymphoid tissues initiates T cell dependent humoral immune responses. As a consequence of this primary B cell activation, germinal center (GC) cell precursors migrate into B cell follicles where they engage T cells and follicular dendritic cells (FDC), and differentiate into plasma cells or memory B cells. Both the homing of B cells to the GC and their interaction with FDC critically depend on integrin-mediated adhesion. We have recently identified the growth and motility factor, hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, the c-met-encoded receptor tyrosine kinase, as a novel paracrine signaling pathway regulating B cell adhesion within the GC microenvironment [22]. The c-Met protein is expressed on B cells localized in the dark zone of the GC (centroblasts) and is induced by combined CD40 and B-cell receptor ligation. Stimulation of c-Met with HGF/SF, which is produced at high levels by tonsillar stromal cells and FDC, leads to enhanced integrin-mediated adhesion of B cells to fibronectin and VCAM-1 [22].
Advances in Experimental Medicine and Biology | 1993
Gerrit Koopman; Robert M. J. Keehnen; Steven T. Pals
Germinal centers play a key role in the maturation of the B cell immune response. Although the initial B cell triggering after interaction of the immunoglobulin receptor molecule with the antigen is thought to take place in the paracortical areas of lymph node and MALT, the isotype switch, affinity maturation and differentiation of B cells into memory cells all take place in the germinal center1-3. B cells that enter the germinal center divide rapidly. Through the process of somatic hypermutation a great heterogeneity in antigen binding specificity in the proliferating B cell population is generated4. However only cells with Ig receptors with high affinity for the antigen are selected for further maturation into memory cells, while the non selected cells die through a process of programmed cell death (PCD)5,6. PCD, also called apoptosis constitutes a cell elimination program, that involves generation of DNA strand breaks, chromatin condensation and cell fragmentation.
Immunology Letters | 1997
R. van der Voort; Taher E.I. Taher; Robert M. J. Keehnen; C. Smit; M. Groenink; Steven T. Pals
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Blood | 1994
Gerrit Koopman; C. P. M. Reutelingsperger; G. A. M. Kuijten; Robert M. J. Keehnen; Steven T. Pals; M. H. J. Van Oers
Journal of Immunology | 1994
Gerrit Koopman; Robert M. J. Keehnen; Ernst Lindhout; Walter Newman; Yoji Shimizu; G A van Seventer; C.H. de Groot; Steven T. Pals
Blood | 2002
Patrick W. B. Derksen; Robert M. J. Keehnen; Ludo M. Evers; Marinus H. J. van Oers; Marcel Spaargaren; Steven T. Pals
Journal of Experimental Medicine | 1997
Robbert van der Voort; Taher E.I. Taher; Robert M. J. Keehnen; Lia Smit; Martijn Groenink; Steven T. Pals
European Journal of Immunology | 1997
Gerrit Koopman; Robert M. J. Keehnen; Ernst Lindhout; David F. H. Zhou; Cornelis de Groot; Steven T. Pals
Journal of Experimental Medicine | 2000
Robbert van der Voort; Robert M. J. Keehnen; Esther A. Beuling; Marcel Spaargaren; Steven T. Pals
European Journal of Immunology | 1996
Susanne M. A. Lens; Robert M. J. Keehnen; Marinus H. J. van Oers; René A. W. van Lier; Steven T. Pals; Gerrit Koopman