Junctional epidermolysis bullosa (JEB) is a severe and often lethal genetic disease caused by mutations in genes encoding the basement membrane component laminin-332. Surviving patients with JEB develop chronic wounds to the skin and mucosa, which impair their quality of life and lead to skin cancer. Here we show that autologous transgenic keratinocyte cultures regenerated an entire, fully functional epidermis on a seven-year-old child suffering from a devastating, life-threatening form of JEB. The proviral integration pattern was maintained in vivo and epidermal renewal did not cause any clonal selection. Clonal tracing showed that the human epidermis is sustained not by equipotent progenitors, but by a limited number of long-lived stem cells, detected as holoclones, that can extensively self-renew in vitro and in vivo and produce progenitors that replenish terminally differentiated keratinocytes. This study provides a blueprint that can be applied to other stem cell-mediated combined ex vivo cell and gene therapies.

The ␤ 2 integrins are important for transendothelial migration of leukocytes as well as for T-cell activation during antigen presentation. Despite abundant expression of ␤ 2 integrins on antigen-presenting cells (APCs), their functional relevance for antigen presentation is completely unclear. We show here that dendritic cells (DCs) from CD18-deficient mice, which lack all functional ␤ 2 integrins, have no defect in antigen presentation. Moreover, DCs from normal mice express inactive ␤ 2 integrins that do not become activated on contact with T cells, at least in vitro. Pharmacologic activation of ␤ 2 integrins on DCs results in a significant reduction of their T cell-activating capacity. This effect is mediated by Mac-1 (CD11b/CD18) on DCs because it could be reversed via blocking antibodies against CD18 and CD11b. Furthermore, the antigen-presenting capacity of macrophages, which express constitutively active ␤ 2 integrins, is significantly enhanced on Mac-1 blockade. We therefore conclude that active CD11b/ CD18 ( IntroductionThe ␤ 2 integrins (CD11/CD18) are heterodimeric leukocyte adhesion molecules exclusively expressed on hematopoietic cells. They play an important role for cell-to-cell contacts between leukocytes as well as for contacts between leukocytes and endothelial cells. 1,2 The common ␤ chain (CD18) associates with 4 different ␣ subunits, ␣L, ␣M, ␣X, and ␣D, forming distinct functional heterodimers termed leukocyte functional antigen-1 (LFA-1, CD11a/CD18), Mac-1 (CD11b/CD18), gp150,95 (CD11c/CD18), and CD11d/CD18. [2][3][4] These interact with more than 20 ligands, many of which belong to the family of ICAMs. 5,6 Adhesion between T cells and antigen-presenting cells (APCs) is necessary for the formation of the immunologic synapse (IS). 7,8 Interactions between LFA-1 on the surface of T cells and intercellular adhesion molecules ICAM-1, 2, and 3 (in humans) on the APC surface were described to be involved in formation of the IS. 9,10 Moreover, ligation of LFA-1 on T cells is required for optimal activation and differentiation of T cells, [11][12][13][14][15][16][17][18][19][20][21] although the downstream signaling events are still not fully understood. On T cells, experiments with blocking antibodies against LFA-1 and with LFA-1-deficient T cells have shown that those T cells are impaired in numerous effector functions. [22][23][24] Dendritic cells (DCs), on the other hand, are known to be the most relevant APCs in the immune system. 25,26 DCs express at least 3 ␤ 2 integrins, LFA-1 (CD11a/CD18), Mac-1 (CD11b/ CD18), and gp150,95 (CD11c/CD18). 27,28 Compared to LFA-1 on T cells, very little information is available about the role and function of ␤ 2 integrins on DCs, especially regarding the process of antigen presentation and T-cell activation. Studies with splenocytes of mice deficient in CD11a, CD11b, CD11c, and CD11d showed impaired T-cell activation in CD11a-, CD11b-, and CD11d-deficient splenocytes on stimulation with superantigen, but this was due to dysfunctional T cells rather than a de...

SUMMARYRespiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants under 6 months of age. Since an RSV infection does not necessarily prevent a reinfection, we asked whether RSV might subvert an effective immune response by interfering with the function of dendritic cells (DCs). Immature DCs cultured from cord blood stem cells and infected with RSV reduced the rate of interferon-g (IFN-g) production in co-cultured autologous naõ Ève T cells stimulated with the superantigen TSST-1. Maturation of DCs in response to poly(IC) but not to CD40 ligand did overcome the inhibitory effect of RSV. Further experiments demonstrated that induction of apoptosis, a selective increase in CD86 expression and lack of release of proin¯ammatory cytokines were associated with inhibition of IFN-g generation. In addition, RSV replication seemed to be essential for modulation of IFN-g production because a virus preparation inactivated by UV irradiation had no effect. Hence, one reason for multiple reinfections by RSV might be the subversion of antiviral immune responses by interference of RSV with DC function.

Highlights d YAP sustains epidermal stem cells d LAMB3-dependent JEB leads to YAP inactivation and epidermal stem cell depletion d JEB cell and gene therapy rescue adhesion, YAP, and stem cells in vitro and in vivo d Enforced YAP rescues stem cells in the absence of cell adhesion