Hearts from alpha1,3-galactosyltransferase knockout pigs (GalT-KO, n = 8) were transplanted heterotopically into baboons using an anti-CD154 monoclonal antibody-based regimen. The elimination of the galactose-alpha1,3-galactose epitope prevented hyperacute rejection and extended survival of pig hearts in baboons for 2-6 months (median, 78 d); the predominant lesion associated with graft failure was a thrombotic microangiopathy, with resulting ischemic injury. There were no infectious complications directly related to the immunosuppressive regimen. The transplantation of hearts from GalT-KO pigs increased graft survival over previous studies.

The use of animal organs could potentially alleviate the critical worldwide shortage of donor organs for clinical transplantation. Because of the strong immune response to xenografts, success will probably depend upon new strategies of immune suppression and induction of tolerance. Here we report our initial results using alpha-1,3-galactosyltransferase knockout (GalT-KO) donors and a tolerance induction approach. We have achieved life-supporting pig-to-baboon renal xenograft survivals of up to 83 d with normal creatinine levels.

IntroductionHuman hematopoietic tissue and cell transplantation into immunodeficient mice, such as mice with the severe combined immunodeficiency (SCID) 1,2 mutation and their derivatives, including NOD/SCID, 3 NOD/SCID/␤2m null , 4 and NOD/SCID/ ␥c null mice, 5 has been widely used to study the function of human immune cells. However, only a few studies have shown the ability to achieve systemic in vivo immune responses in humanized mice. 6 In general, immunodeficient mice that received a transplant of human hematopoietic stem cells (HSCs) have poor human T-cell development. Although some human T-cell reconstitution was seen in NOD/SCID/␥c null mice after human umbilical cord blood (UCB) stem-cell transplantation, human thymopoiesis in the recipient thymus appeared inefficient, and the mouse thymus remained underdeveloped in these mice. 5 Recently, Traggiai et al 6 reported that intrahepatic injection of human CD34 ϩ UCB cells into newborn Rag2 Ϫ/ Ϫ␥c Ϫ/Ϫ mice results in improved human T-cell development in the mouse thymus. An important advancement in this model compared with UCB transplantation in adult mice was the ability of grafted mice to mediate in vivo antiviral immune responses. 6 However, a long period of time (16 weeks) was required to achieve significant peripheral human T-cell repopulation in these mice, and the levels of human T cells in the spleen of long-term surviving mice were relatively low. Furthermore, the MHC restriction and tolerance status of human T cells that were selected in the mouse thymus in these mice still remains undefined.A commonly used mouse model for the study of human For personal use only. on June 19, 2019. by guest www.bloodjournal.org From Materials and methods Animals and human fetal tissuesImmunodeficient nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice were housed in a specific pathogen-free microisolator environment and used at 6 to 10 weeks of age. Human fetal thymus and liver tissues of gestational age of 17 to 20 weeks were obtained from Advanced Bioscience Resource (Alameda, CA). Inbred Massachusetts General Hospital miniature swine (kindly provided by David H. Sachs) 10 were used as porcine skin donors. Protocols involving the use of human tissues and animals were approved by the Massachusetts General Hospital Human Research Committee and Subcommittee on Research Animal Care, and all of the experiments were performed in accordance with the protocols. Human tissue implantationMice were conditioned with sublethal (2-3 Gy) whole-body irradiation. Human fetal Thy and Liv fragments measuring about 1 mm 3 were implanted under the recipient kidney capsule within 3 days after irradiation. Some mice also received CD34 ϩ FLCs (1-5 ϫ 10 5 /mouse, intravenously) purified from the same donor on the day of human Thy/Liv transplantation. CD34 ϩ FLCs were isolated by the magnetic-activated cell sorter (MACS) separation system using anti-CD34 microbeads (Miltenyi Biotec, Auburn, CA). Levels of human hematopoietic cells in the mice that underwent transplantation ...

The sophisticated microarchitecture of the lymph node, which is largely supported by a reticular network of fibroblastic reticular cells (FRCs) and extracellular matrix, is essential for immune function. How FRCs form the elaborate network and remodel it in response to lymphocyte activation is not understood. In this work, we established ERTR7 ϩ gp38 ϩ VCAM-1 ϩ FRC lines and examined the production of the ER-TR7 antigen. Multiple chemokines produced by FRCs induced T cell and dendritic cell chemotaxis and adhesion to the FRC surface. FRCs can secrete the ER-TR7 antigen as an extracellular matrix component to make a reticular meshwork in response to contact with lymphocytes. The formation of the meshwork is induced by stimulation with tumor necrosis factor-␣ or lymphotoxin-␣ in combination with agonistic antibody to lymphotoxin-␤ receptor in a nuclear factor-B (RelA)-dependent manner. These findings suggest that signals from lymphocytes induce FRCs to form the network that supports the movement and interactions of immune effectors within the lymph node.