Technique of endoscopic biopsy of islet allografts transplanted into the gastric submucosal space in pigs.

Currently, islet cells are transplanted into the liver via portal vein infusion. One disadvantage of this approach is that it is not possible to adequately biopsy the islets in the liver to assess for rejection. Islet transplantation (Tx) into the gastric submucosal space (GSMS) can be performed endoscopically and has the potential advantage of histological evaluation by endoscopic biopsy. The aim of this study was to determine whether a representative allograft sample could be obtained endoscopically. We performed islet Tx into the GSMS in nonimmunosuppressed pigs using simple endoscopic submucosal injection. Islets were transplanted at four sites. Endoscopic ultrasonography and biopsy of the transplanted islets at two sites by modified endoscopic submucosal dissection were carried out successfully in all pigs 5 days after islet Tx. Tissue obtained at both biopsy and necropsy (including full-thickness sections of the gastric wall around the sites of the remaining islets and biopsies) were examined by histology and immunohistochemistry to confirm the presence of the islet grafts and any features of rejection. Representative allograft sampling was successfully obtained from all biopsy sites. All biopsies included islets with insulin-positive staining. There was significant CD3(+) and CD68(+) cell infiltration in the islet masses obtained at biopsy and from sections taken at necropsy, with similar histopathological features. Endoscopic biopsy of islet allografts in the GSMS is feasible, provides accurate histopathological data, and would provide a significant advance if translated into clinical practice.

A syndrome of severe hypoglycemia and acidosis in young immunosuppressed diabetic monkeys and pigs-association with sepsis.

BACKGROUND: Large animals treated with immunosuppressive drugs for preclinical experiments of transplantation have increased risks of infection, which can be compounded by the induction of diabetes if islet transplantation is planned. METHODS: We report our experience with severe sepsis in two young cynomolgus monkeys and five pigs that were subjected to diabetes induction, immunosuppressive therapy, or islet allotransplantation. RESULTS: In two monkeys and five pigs, infection was associated with a syndrome of profound hypoglycemia accompanied by severe acidosis, which was resistant to treatment. We do not believe that this syndrome has been reported previously by others. CONCLUSIONS: Despite treatment, this syndrome complicated the interpretation of blood glucose readings as a measure of islet graft function and resulted in death or the need for euthanasia in all seven animals. We tentatively suggest that the syndrome may be related to the presence of microorganisms that metabolize glucose and produce lactate.

Platelet aggregation in humans and nonhuman primates: relevance to xenotransplantation.

INTRODUCTION: Platelet activation/aggregation plays a key role in the dysregulation of coagulation and the development of thrombotic microangiopathy in nonhuman primate recipients of pig xenografts. As a preliminary to the study of anti-platelet therapy in vitro and in vivo, the present study aimed to compare platelet aggregation in whole blood from humans, baboons, and cynomolgus monkeys. METHODS: Using "Chrono-log" technology (two-sample four-channel Chrono-log Whole Blood Aggregometer), we studied aggregation of platelets in healthy humans (n = 8), baboons (n = 5), and monkeys (n = 8). Whole blood (WB) samples were collected, and platelet aggregation was assessed using three different volumes of blood (1, 0.5, and 0.25 ml). Platelet activation was induced using collagen (at 3 and 5 µg/ml), ristocetin (at 0.5 and 1.0 mg/ml), adenosine diphosphate (ADP; at 10, 20, and 40 µm), or thrombin (at 1 and 5 IU/ml). Inhibition of agonist-induced platelet aggregation by heparin and low molecular weight heparin (LMWH) (at 1, 10, and 100 IU/ml) was evaluated. RESULTS: Mean platelet counts were 222.1, 263.2, and 276.1 (×10(3) /µl) in humans, baboons, and monkeys, respectively. In all three species, platelet aggregation was induced by collagen, ristocetin, ADP, or thrombin in a dose-dependent manner. A blood volume of 0.5 ml provided the most consistent results with all agonists in all three species. Dilution studies indicated that there was a significant positive correlation between platelet count and percent aggregation of platelets (P < 0.05). Collagen (3 and 5 µg/ml), ADP (10, 20, and 40 µm), and thrombin (1 and 5 IU/ml) induced significantly greater platelet aggregation in humans than in baboons. ADP (20 and 40 µm) and thrombin (1 and 5 IU/ml) induced significantly greater platelet aggregation in monkeys than in baboons. There was no species difference with ristocetin (0.5 or 1.0 mg/ml). In all species, thrombin (1 or 5 IU) induced greater platelet aggregation than any of the other reagents. Heparin at 1 IU/ml and LMWH at 10 IU/ml in all species almost completely abrogated thrombin-induced platelet aggregation. Heparin at 100 IU/ml effectively inhibited platelet aggregation induced by collagen, but only partially inhibited aggregation induced by ADP or ristocetin. LMWH only partially inhibited aggregation induced by collagen, ristocetin, and ADP. CONCLUSIONS: The "Chrono-log" technology proved to be a reliable method of evaluating platelet activation and aggregation in vitro in primates. Species differences may play a role in platelet aggregation, with the monkey being more comparable to the human than the baboon, although overall trends were similar. In all species, thrombin induced greater platelet aggregation than other agonists. Even a concentration of heparin of 1 IU/ml, which is probably the maximal concentration that is clinically-applicable, prevented platelet aggregation induced by thrombin, but was less effective in preventing aggregation induced by collagen, ADP, or, particularly, ristocetin.

T-cell-based immunosuppressive therapy inhibits the development of natural antibodies in infant baboons.

BACKGROUND: We set out to determine whether B-cell tolerance to A/B-incompatible alloantigens and pig xenoantigens could be achieved in infant baboons. METHODS: Artery patch grafts were implanted in the abdominal aorta in 3-month-old baboons using A/B-incompatible (AB-I) allografts or wild-type pig xenografts (pig). Group 1 (Gp1) (controls, n=6) received no immunosuppressive therapy (IS) and no graft. Gp2 (n=2) received an AB-I or pig graft but no IS. Gp3 received AB-I grafts+IS (Gp3A: n=2) or pig grafts+IS (Gp3B: n=2). IS consisted of ATG, anti-CD154mAb, and mycophenolate mofetil until age 8 to 12 months. Gp4 (n=2) received IS only but no graft. RESULTS: In Gp1, anti-A/B and cytotoxic anti-pig immunoglobulin-M increased steadily during the first year. Gp2 became sensitized to donor-specific AB-I or pig antigens within 2 weeks. Gp3 and Gp4 infants that received anti-CD154mAb made no or minimal anti-A/B and anti-pig antibodies while receiving IS. DISCUSSION: The production of natural anti-A/B and anti-pig antibodies was inhibited by IS with anti-CD154mAb, even in the absence of an allograft or xenograft, suggesting that natural antibodies may not be entirely T-cell independent. These data are in contrast to clinical experience with AB-I allotransplantation in infants, who cease producing only donor-specific antibodies.

Collagenous colitis-like condition in immunosuppressed infant baboons.

BACKGROUND: Collagenous colitis is a chronic inflammatory bowel disease of unknown etiology. It is fairly common in adult humans, but rare in infants, and has been associated with autoimmune disorders. METHODS: We report four infant baboons (age 7-12 months) that had received a transplant at 3 months of age and subsequent immunosuppressive therapy for periods of 4-10 months. All presented identical symptoms within a period of 4 weeks, including weight loss associated with chronic watery diarrhea that was unresponsive to standard antimicrobial treatment. RESULTS: Clinical chemistry evaluations were within normal ranges, viral causes were ruled out, and fecal and blood cultures were repeatedly negative. At necropsy, two infant baboons were found to have a form of collagenous colitis. In the remaining two baboons that had identical clinical features, immunosuppressive therapy was discontinued and treatment with budesonide was initiated. Both baboons recovered and remained well on no medication until the end of follow-up (24 months). CONCLUSIONS: Collagenous colitis has occasionally been reported in patients with organ transplants. It has been reported only once previously in baboons. The four cases reported here strongly suggest that 1) clinical features as well as histopathological findings of collagenous colitis in baboons are very similar to those in human patients; 2) it was associated with the immunocompromised state of the baboons, as two nonimmunosuppressed age-matched baboons in close proximity did not develop the condition; and 3) it may have had an infectious origin, as all four cases developed within a 4-week period of time.

Induced regulatory T cells: mechanisms of conversion and suppressive potential.

Thymus-derived, naturally occurring CD4(+) Forkhead Box P3(+) regulatory T cells (nTreg) have suppressive activity that is important for the establishment and maintenance of immune homeostasis in the healthy state. Abundant reports have demonstrated that they can suppress pathogenic processes in autoimmune diseases and inhibit transplant rejection and graft-versus-host disease. Far less is known about induced regulatory T cells (iTreg) that are generated from naive T cells in the periphery or in vitro by directing naive T cells to acquire suppressive function under the influence of transforming growth factor-ß and other factors. In this review, we describe mechanisms by which naive T cells are thought to be converted into iTreg. We also discuss the suppressive potential of iTreg, particularly in comparison with their naturally occurring counterparts, focusing on those reports in which direct comparisons have been made. Based on current knowledge, we consider the rationale for using iTreg versus nTreg in clinical trials.

T-lymphocyte homeostasis and function in infant baboons: implications for transplantation.

Laboratory mice are born lymphopenic and demonstrate lymphopenia-induced proliferation that generates memory T cells, yet they are prone to immunologic tolerance. Here we tested whether these fundamental immunologic observations apply to higher animals by studying the immune system of infant baboons. Using flow cytometry of the peripheral blood cells, it was found that baboons are born relatively lymphopenic and subsequently expand their initially naïve T cell pool with increasing numbers of memory T cells. After transplantation of an artery patch allograft or xenograft, non-immunosuppressed recipients readily mounted an immune response against donor-type antigens, as evidenced by mixed lymphocyte reaction. Immunosuppression with anti-thymocyte globulin (ATG), anti-CD154 mAb, and mycophenolate mofetil prevented T cell-mediated rejection. After lymphocyte depletion with ATG, homeostatic T cell proliferation was observed. In conclusion, the baboon proved a suitable model to investigate the infant immune system. In this study, neonatal lymphopenia and expansion of the memory T cell population were observed but, unlike mice, there were no indications that infant baboons are prone to T cell tolerance. The expansion of memory T cells during the neonatal period or after induction therapy may actually form an obstacle to tapering immunosuppressive therapy, or ultimately achieving immunologic tolerance.

Non-human primate regulatory T cells: current biology and implications for transplantation.

Regulatory T cells (Treg) offer potential for improving long-term outcomes in cell and organ transplantation. The non-human primate model is a valuable resource for addressing issues concerning the transfer of Treg therapy to the clinic. Herein, we discuss the properties of non-human primate Treg and prospects for their evaluation in allotransplantation and xenotransplantation.

Hepatic function after genetically engineered pig liver transplantation in baboons.

BACKGROUND: If "bridging" to allo-transplantation (Tx) is to be achieved by a pig liver xenograft, adequate hepatic function needs to be assured. METHODS: We have studied hepatic function in baboons after Tx of livers from alpha1,3-galactosyltransferase gene-knockout (GTKO, n=1) or GTKO pigs transgenic for CD46 (GTKO/CD46, n=5). Monitoring was by liver function tests and coagulation parameters. Pig-specific proteins in the baboon serum/plasma were identified by Western blot. In four baboons, coagulation factors were measured. The results were compared with values from healthy humans, baboons, and pigs. RESULTS: Recipient baboons died or were euthanized after 4 to 7 days after internal bleeding associated with profound thrombocytopenia. However, parameters of liver function, including coagulation, remained in the near-normal range, except for some cholestasis. Western blot demonstrated that pig proteins (albumin, fibrinogen, haptoglobin, and plasminogen) were produced by the liver from day 1. Production of several pig coagulation factors was confirmed. CONCLUSIONS: After the Tx of genetically engineered pig livers into baboons (1) many parameters of hepatic function, including coagulation, were normal or near normal; (2) there was evidence for production of pig proteins, including coagulation factors; and (3) these appeared to function adequately in baboons although interspecies compatibility of such proteins remains to be confirmed.

Parental fever attitude and management: influence of parental ethnicity and child's age.

OBJECTIVE: The objective was to study parental fever management and attitude toward fever from the perspective of the child's ethnicity and age. PATIENTS AND SETTING: Children with fever presenting at the pediatric emergency department (PED) of the Erasmus MC-Sophia Children's Hospital, Rotterdam, the Netherlands, in the period from February 2002 to March 2004. DESIGN: Prospective observational. MAIN OUTCOME MEASURES: Parental fever attitude and management assessed by a questionnaire. RESULTS: Two hundred eleven children with fever (median age, 1.2 years; interquartile range, 0.7-2.0 years) were included, of whom 108 (55%) were boys. One hundred fourteen children (54%) were self-referrals at the PED. Accompanying symptoms were reported in 95% (50% had > or = 3); median temperature measured at PED was 39.5 degrees C (interquartile range, 38.9 degrees C-40.8 degrees C). One hundred fifty-five parents (74%) had used antipyretics to reduce fever, and 155 parents (74%) were worried about fever and its possible complications. Differences between Dutch and non-Dutch ethnicities were seen in temperature-reducing techniques, self-referral, and parental anxiety of fever and its complications. Age did not influence parental fever attitude and management. CONCLUSIONS: For most children in our population, the use of antipyretics was justified, as the majority of our children visiting the PED for an acute febrile episode are young infants, in particular with a high degree of fever and accompanying symptoms. We confirm and extend previous findings of ethnicity influencing parental fever management.