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Prof. Yvonne Samstag and her co-workers investigate molecular mechanisms that regulate the activation, polarisation and migration of human T-lymphocytes. The group currently focusses on the importance of actin-binding proteins as key molecules for these processes. T-lymphocytes continuously circulate through the body. Recognition of dangerous structures (antigens) occurs at the contact zone between T-lymphocytes and antigen-presenting cells. This contact zone is called the immunological synapse. The group has shown that the actin-reorganizing protein cofilin (Fig. 1) and the actin-bundling protein L-plastin (Fig. 2) are essential for formation of the immunological synapse and the activation of human T-lymphocytes. Via expression of EGFP-fusion proteins it could be demonstrated that L-plastin is one of the first molecules that translocate to the contact zone between T-cells and antigen-presenting cells (Fig. 2).


Fig.1: Cofilin enriches in the immune synapse between T cells and antigen-presenting B cells  

(confocal laserscanning microscopy): Human T-lymphocytes from peripheral blood (T) were incubated with superantigen loaded Raji B-cells (SEB/SEF) or unloaded Raji B-cells (no Ag). After fixation cofilin was stained in green (Cy2) and the T-cell receptor/CD3 complex was stained in red (Cy3).


Fig.2 (Video): L-Plastin translocates within seconds to the T-cell/APC contact zone

(Time-Lapse-Video microscopy): Via transfection of cDNA, an L-Plastin-EGFP fusion protein was expressed in human T-lymphocytes from peripheral blood. Then these cells (small cells) were incubated with superantigen loaded Raji B-cells (large cells). The video shows the digital interference contrast of the cells (DIC, upper panel) and the fluorescence of L-Plastin-EGFP in “pseudocolours” (lower panel). Dark (blue) colours represent low while bright (red to white) colours represent high relative local L-plastin concentrations. The movie was prepared from single pictures that were acquired in time gaps of 18 seconds.


Currently, we characterize the signal cascades and the post-translational modifications that regulate the activities of cofilin and L-plastin. To this end, a broad range of reagents and cDNA-constructs as well as cell biological and biochemical methods for the analysis of intracellular molecules, T-lymphocyte migration, T-lymphocyte polarization and T- lymphocyte activation have been established. These include cell transfection and the analysis of the cells by confocal laser-scanning microscopy (Fig.1), time-lapse video-microscopy (Fig. 2) and flow cytometry. Our work is supported by grants of the Deutsche Forschungsgemeinschaft (SFB 405 / A4 and DFG SA393/3). The special aim of the advertised project is the analysis of the function and regulation of cofilin and L-plastin in different leukocyte subsets (B-lymphocytes, NK-cells, mast cells, macrophages and dendritic cells). This work will be performed in close cooperation with the other groups involved in this PhD-program.


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Prof. Dr. Yvonne Samstag

Institut für Immunologie

Ruprecht-Karls-Universität Heidelberg

Im Neuenheimer Feld 305

D-69120 Heidelberg, Germany

e-mail: yvonne.samstag(at)urz.uni-heidelberg.de