FasL promotes cell conjugates formation in CD4+ T lymphocytes.

<p>Contour plots show CD4+ T cells untreated (A) and treated with FasL (B) for 30 min. The treatment increases the percentage of cell conjugates identified by gate R2 drawn on physical parameters of scattering (FSC/SSC). Statistical analysis of CD4+ T cells shows the percentage of cell conjugates at different times with (Fas-L) or without (CTRL) FasL treatment (C). The histogram highlights that FasL administration led a sharp increase of cell conjugates within 30 min, slightly decreasing later. * indicates statistical significance: p<0.05 (n = 6 experiments). The formation of cell conjugates after FasL treatment is also documented by confocal microscopy (D–F). CD4+ T cells were labelled with CFSE (green) and DiI (red). In control condition (D), the cells appear isolated with distinct fluorescences, whereas in the FasL samples (E,F) the cells are tightly linked with mixed fluorescences. These observations attest an intercellular exchange of DiI+ and/or CFSE+ patches.