Finally an important practical implication

Finally, an important practical implication of our data is that both fibroblasts and blood can be used for the generation of comparable iPSC lines for large-scale biobanking purposes (Figure 6). Our results demonstrate that variability among small cohorts of iPSCs may lead to erroneous conclusions (Sandoe and Eggan, 2013). Because of the inherent differences resulting from the donor-dependent variability, it seems obvious that relatively large cohorts of iPSC lines from different donors, rather than several isogenic clones from a few donors, would be needed to obtain reliable results concerning the impact of donor-specific variants. However, the fact that intra-individual clonal variation is still present after careful technical standardization and iPSC characterization also suggests that genetically matched clones from the donor should be available in biobanks.
Experimental Procedures
Author Contributions
Acknowledgments This work was supported by the Academy of Finland (Grant No. 141482 and No. 257157), the Sigrid Juselius Foundation, Research Funds of the Helsinki University Central Hospital, The Swedish Research Council, AFA Insurance (Sweden), Lund University Medical Faculty, the HematoLinné Program Grant, Stem Therapy Program Grant, and the Crafoord Foundation (N.-B.W.). J.K. was supported through funds from the Academy of Finland (grant No. 283045). We thank Ms. Anne Nyberg for excellent technical assistance. We thank participants of the Takotsubo study, and Dr. Robert Leigh for constructive comments and proofreading of the manuscript. Roksana Moraghebi and Cristina Valensisi contributed equally to the study.
Introduction Cytotoxic T lymphocytes (CTLs) play a crucial role in the eradication of cancer GS-9620 by precisely recognizing them via tumor antigen-specific T cell receptors (TCRs) in a peptide-dependent, human leukocyte antigen (HLA)-restricted manner (Maus et al., 2014). Sometimes, however, cancer cells can proliferate due to absent or dysfunctional CTLs, thus creating demand for immunotherapies. We and another group recently reported the unlimited production of target antigen-specific human CD8+ T lymphocytes from induced pluripotent stem cells (iPSCs) (Nishimura et al., 2013; Vizcardo et al., 2013). This technology has the potential to overcome two important problems currently facing T cell immunotherapies: a shortage of tumor antigen-specific T cells and their exhaustion induced by continuous TCR stimulation and overproliferation (Schietinger and Greenberg, 2014). However, other problems in T cell immunotherapies must also be overcome. One example is the emergence of tumor escape from antigen-specific monoclonal CTLs due to tumor immune-editing involving tumor antigen mutagenesis or HLA depression (Schreiber et al., 2011). Another problem is local immunosuppression in the tumor microenvironment by instigated immune cells, which supports tumor growth and inhibits CTL activities (Mittal et al., 2014; Motz and Coukos, 2013; Noy and Pollard, 2014). A good approach to overcome these problems would be combination therapy using a cellular adjuvant, i.e., invariant natural killer T (iNKT) cells, as iNKT cells exert helper functions to induce antigen-specific polyclonal CTLs (Cerundolo et al., 2009), improve the immunosuppressive milieu (De Santo et al., 2010), and maintain memory CD8+ T cells (Hong et al., 2009). iNKT cells are a unique subset of T cells that express a canonical invariant TCR α chain (Vα24-Jα18 in humans) and TCR β chains that use limited Vβ segments (Vβ11 in humans), and also play a key role in the regulation of innate and adaptive immunity (Berzins et al., 2011; Brennan et al., 2013). In contrast to conventional αβ T cells, iNKT cells recognize a limited number of lipid antigens presented by the MHC class I-like molecule CD1d. Stimulation of iNKT cells by α-galactosylceramide (α-GalCer), a synthetic glycosphingolipid, results in the rapid production of Th1 and Th2 cytokines (e.g., interleukin-γ [IFN-γ] and interleukin-4 [IL-4]) and increased expression of CD40 ligand (CD40L), which induces dendritic cell (DC) maturation and production of IL-12p70 (Liu et al., 2008; McEwen-Smith et al., 2015; Uemura et al., 2009). These events ultimately lead to downstream activation of critical effectors of antitumor immunity, including NK cells, CTLs, and Th cells (Hong et al., 2009; Salio et al., 2014). Because CD1d is non-polymorphic, the modification of DC function by iNKT cells is independent of HLA restriction, making this process attractive for broad clinical application.