Supplementary MaterialsTransparent reporting form. cause leukocyte adhesion deficiency type-III (LAD-III) syndrome, which is characterized by severe bleedings, infections and accumulation of HSPCs in the blood circulation (Kuijpers et al., 2009; Malinin et al., 2009; Mory et al., 2008; Ruppert et al., 2015; Svensson et al., 2009). In the present study, we investigated T-lymphopoiesis Aprotinin in kindlin-3-deficient mice. We found that loss of kindlin-3 protein expression results in progressive thymus atrophy, which is mainly caused by impaired colonization of the vascularised thymus by BM-derived T cell progenitors during late embryogenesis and after birth. In contrast, however, colonization of the non-vascularized thymic primordium by kindlin-3-deficient FL-derived progenitors proceeded without kindlin-3, albeit less efficiently, due to the lower vascular shear flow in embryos. Within the thymus anlage, the proliferation rate of kindlin-3-deficient T cell populations was reduced, while differentiation into mature CD4 and CD8 T cells was unaffected. Thus, these findings clearly show the crucial role of integrins during T cell development. Specifically, in the absence of kindlin-3 only a weak integrin-mediated T cell adhesion can occur, which suffices resistance to low systemic shear forces and enables T cell progenitor homing early during development. However, at later time points during development, when vascular shear forces increase, kindlin-3 is critical to stabilize T cell adhesion on endothelial cells allowing T cell progenitor homing into the thymus. Results Loss of kindlin-3 protein leads to progressive thymus atrophy Kindlin-3 is expressed in CD4/CD8 double negative (DN) and double positive (DP) T cells from wild-type (WT) thymi and SP CD4 and CD8 T cells from WT spleens (Figure 1figure supplement 1A). To test whether kindlin-3 expression is required for thymopoiesis, we investigated thymus morphology and size in kindlin-3-deficient (and mice were stained with CFSE and stimulated either with DCs loaded with different concentrations of MOG35-55 peptide or primed with anti-CD3e/CD28 antibodies and PMA. Representative histograms show CSFE dilution. Red-lined histograms represent cells incubated Aprotinin with not-loaded DCs or no antibodies. Bars indicate means??standard errors. **pmice, and measured CSFE Rabbit Polyclonal to SCNN1D dilution by flow cytometry. In line with the observation that thymi.Thymocytes from by injecting polyIC into mice and detected almost no DN (Linneg) cells in their thymi, whereas control thymi from polyIC-treated Aprotinin hypomorphic (n/-) mice that have been labelled with CFSE and Far Red and mixed in a 1:1 ratio. Grey line represents isotype control. (H,I) Adhesion of CD4+ T cells in vivo. (H) Representative microscopic images of adherent (+/+, red) and (n/-, green) cells in the lymph node vasculature after adoptive transfer. Sum intensity Z projections of confocal stacks are shown. Segmented lines indicate vessel outlines. Scale bar?=?50 m. (I) Quantification of adherent CD4+ T cells (N?=?18C19 vessels from three mice). (J, K) Microvascular blood flow in the lymph node vasculature. (J) Centerline blood flow velocity and (K) vascular shear rate in LN microvessel segments (N?=?25C27 field of views from three mice). Bars indicate Aprotinin means??standard deviation. **phypomorphic mice (K3n/-), respectively, into recipient Aprotinin mice and analysed their adhesion to the popliteal LN vasculature by spinning disc confocal microscopy (Figure 8G,H). hypomorphic mice express only 5% kindlin-3 protein and therefore show a strong defect in leukocyte adhesion (Klapproth et al., 2015). As expected, we observed a reduced number of adherent hypomorphic T cells in the LN vasculature compared to WT cells (Figure 8H,I). We then injected fluorescent microspheres and measured the blood flow velocities in LN vessel segments and determined shear rates adherent cells.