Signal Transducing Adaptor Protein (STAP) Family Accelerates Gut and Thymic Graft-Versus-Host-Disease in Murine Model

• Published in: Blood 2018-11, Vol.132 (Supplement 1), p.4516-4516
• Main Authors: Saito, Hideaki, Ichii, Michiko, Toda, Jun, Kitai, Yuichi, Muromoto, Ryuta, Kashiwakura, Jun-ichi, Saitoh, Kodai, Shibayama, Hirohiko, Matsuda, Tadashi, Oritani, Kenji, Kanakura, Yuzuru
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2018-99-112803

Graft-versus-host-disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most frequent complication and one of the major causes of non-relapse mortality. However, its pathogenesis has not yet been fully understood. We cloned signal-transducing adaptor protein (STAP)-2 as a c-fms binding protein from a fetal liver library in 2003. The family that contains STAP-1 and STAP-2 has a pleckstrin homology (PH) and Src-homology 2 (SH2)-like domains, suggesting that this adapter protein functions as an immune and inflammatory regulator. Indeed, STAP-2 regulates adhesion and chemotaxis in T cells (Sekine et al., J Immunol. 2009). In this study, we aimed to elucidate the roles of STAP family in GVHD. First, we examined the expression of STAP-1 and STAP-2 mRNA in various human hematopoietic subsets, including CD34+ CD38- hematopoietic stem cells (HSCs), CD34+ CD38+ hematopoietic progenitor cells (HPCs), CD19+ CD27- naïve B cells, CD19+ CD27+ memory B cells, CD3+ CD4+ helper T-cells, and CD3+ CD8+ cytotoxic T lymphocytes, using real-time PCR. As a result, STAP-1 and STAP-2 were expressed in lymphoid cells, as well as HSCs and HPCs. STAP-2 mRNA was highly expressed in T cells. Next, to investigate the role of STAPs in GVHD, we made an experimental murine model. To study the pathogenesis of immune reconstitution and tolerance after allo-HSCT, lethally irradiated BALB/c mice were injected with T and B cell-depleted bone marrow cells (5×106 cells) derived from syngeneic BALB/c or allogeneic C57BL/6 mice on day 0. Co-transplantation of splenocytes was not adapted in this model. Survival and clinical degree of GVHD were assessed by a scoring system that sums changes in 5 clinical parameters: body weight (BW) loss, posture, activity, fur texture, and skin integrity. Recipients transplanted from allogenic wild type (WT) C57BL/6 donor survived without suffering from severe GVHD symptoms, owing to development of immune tolerance against allogeneic antigens. However, compared to syngeneic transplanted mice, these recipients started to show gradual BW loss and GVHD score was increased approximately 28 days after allo-HSCT, indicating the existence of an allogeneic immune reaction. To evaluate the role of STAPs in GVHD, we generated transgenic mice (Tg) that overexpress STAP under the control of Em enhancer and Lck proximal promoter. The promoter could drive expression of the inserted cDNA in lymphoid lineage cells from the common lymphoid pr