B lymphocytes undergo TLR2-dependent apoptosis upon Shigella infection.
Bottom Line: The induction of a type three secretion apparatus (T3SA)-dependent B cell death is observed in the human CL-01 B cell line in vitro, as well as in mouse B lymphocytes in vivo.The presence of bacterial co-signals is required to sensitize B cells to apoptosis and to up-regulate tlr2, thus enhancing IpaD binding.Apoptotic B lymphocytes in contact with Shigella-IpaD are detected in rectal biopsies of infected individuals.
Affiliation: Institut Pasteur, INSERM U786, Unité de Pathogénie Microbienne Moléculaire, 75015 Paris, FranceInstitut Pasteur, INSERM U786, Unité de Pathogénie Microbienne Moléculaire, 75015 Paris, France.Show MeSH
Related in: MedlinePlus
License 1 - License 2
Mentions: As extracellular exposure to IpaD in the presence of bacterial co-signals triggers B cell apoptosis, we assessed IpaD binding to CL-01 B cells. His-tagged IpaD and MxiH were coupled to Alexa Fluor 488 (AF488) and incubated with B cells in the presence of T3SA− bacteria for 2 h at 37°C. Whereas no fluorescence was detected with AF488-MxiH, labeling of B cells was detected upon incubation with AF488-IpaD (Fig. 6 A). As illustrated in Fig. 6 A, the detection of AF488-IpaD in orthogonal slices suggested a specific interaction of IpaD with B cells. To further assess IpaD–CL-01 association, we compared the interaction of AF488-IpaD with these cells in different conditions by measuring relative mean AF488 fluorescence intensities within 15-µm-diameter spheres centered on B cell nuclei. In agreement with results from Fig. 6 A, the relative mean intensity was significantly higher upon incubation at 37°C with IpaD as compared with MxiH (Fig. 6 B). AF488-IpaD relative mean intensity was significantly increased upon incubation at 37°C as compared with 4°C (Fig. 6 B) and with time (Fig. 6 C), suggesting an active internalization process. Indeed, ∼50 and 75% of IpaD bound to B cells at 4°C was internalized after 30 and 60 min incubation at 37°C, respectively (Fig. 6 D). It is noteworthy that the presence of T3SA− bacteria significantly reduced IpaD association after 30 min of incubation with the cells, while significantly increasing it at 24 h after incubation (unpublished data). These findings show that exposure of IpaD to B cells results in its binding and internalization and suggests the existence of a specific interaction partner for IpaD at the B cell surface.
Affiliation: Institut Pasteur, INSERM U786, Unité de Pathogénie Microbienne Moléculaire, 75015 Paris, FranceInstitut Pasteur, INSERM U786, Unité de Pathogénie Microbienne Moléculaire, 75015 Paris, France.