Xenotransplantation: immunological barriers and strategies to overcome them

Hyperacute and acute vascular rejection of xenografts are well defined barriers to clinical pig‐to‐human xenotransplantation. Enormous progress has been made in recent years to overcome these immunological barriers. For example, transgenic expression of human complement regulatory molecules (e.g. CD46, CD55) in pigs has been shown to be an effective strategy to prevent hyperacute rejection in pre‐clinical models of xenotransplantation. Alpha1,3‐galactosyltransferase knock‐out pigs are available and provide a second possibility to avoid hyperacute rejection mediated by pre‐existing antibodies. Furthermore, transfer of protective genes (e.g. A20, HO‐1) to endothelial cells is expected to reduce their susceptibility to effector mechanisms leading to acute vascular rejection. In addition, the efficiency of strategies to avoid coagulation/thrombosis after pig‐to‐human xenotransplantation (e.g. transgenic expression of human thrombomodulin, CD39) is currently tested. Thus, for further development of clinical xenotransplantation immunological concepts are now required facilitating the control of human anti‐pig cellular immune responses. Our group focuses on the inhibition of human anti‐pig T cell responses by targeting “negative” costimulatory pathways. We tested the hypothesis that overexpression of the human negative costimulatory ligands PD‐L1 and PD‐L2 on pig antigen presenting cells will result in reduced human anti‐pig T cell responses. The data so far show that (i) human CD4⁺ T cells respond with reduced proliferation and cytokine synthesis to PD‐L1/PD‐L2 expressing pig cells, (ii) PD‐L1/PD‐L2 pig transfectants induce human regulatory T cells (T_reg) which suppress the activation of conventional T cells, and (iii) PD‐L1/PD‐L2 expressing pig cells are protected from lysis mediated by CD8⁺ human cells. Together these observations support the assumption that transgenic expression of human PD‐L1 and/or PD‐L2 in pig cells and tissues could be an approach to prevent T cell reactivity after pig‐to‐human xenotransplantation. Supported by the Deutsche Forschungsgemeinschaft (Transregio Forschergruppe “Xenotransplantation”, FOR 535).     

Influence of age-related factors on long-term outcome after traumatic brain injury (TBI) in children: A review of recent literature and some preliminary findings

Cerebral plasticity of the immature brain is often inferred to lead to less serious consequences of early traumatic brain injury (TBI) in the pediatric age group. This notion is seriously challenged by recent research findings. Data from prospective studies point to some children's dif-ficulties in ongoing skill-acquisition and the possibility of late-emerging deficits. Accordingly, preliminary group data of an own ongoing study support the notion of an increased risk for pervasive neuropsychological impairment in subjects with severe TBI and early age at trauma. The pattern of neuropsychological deficits may depend on the developmental level at the time of injury, although effects of hemispheric site of lesion were also found to persist in individual cases. Theoretical considerations and empirical findings stress the importance of a longitudinal developmental perspective for the evaluation of long-term outcome after pediatric TBI. ("Verbund Neurotrauma Kiel / Project 4: Evaluation of neurological rehabilitation and course of cognitive development in children and adoles-cents with secondarily acquired brain damage", funded through the Research Program "Gesundheit 2000" of the German government, FKZ 01 KO 9512.)     

On the psychodynamics of an adolescent bulimia patient

The aim is to understand the meaning and significance of the symptoms by means of psychoanalytical theoretical models and to give an insight into the functioning of analytical therapy, using the example of an adolescent bulimia patient. In this therapy, the cause of the bulimic illness is seen as being a failure to build an intrapsychic space, and it is shown how triangulation can be achieved via the three-dimensional analytical relationship. Particular attention is given to the theories of M. Klein and W. R. Bion. The theory of S. Freud is based upon the portrayal of bulimic symptoms as the expression of an intrapsychic conflict. The two models complement each other, leading to a more profound understanding of eating disorders.     

Assessment of functional ability in younger and older patients with ankylosing spondylitis: performance of the bath ankylosing spondylitis functional index

OBJECTIVE: To determine whether the Bath Ankylosing Spondylitis Functional Index (BASFI) is applicable in older patients with ankylosing spondylitis and whether it shows major differences between younger and older patients with ankylosing spondylitis. DESIGN: BASFI total scores and every BASFI item of 202 patients with ankylosing spondylitis aged >or=60 yr (group A) and 267 patients with ankylosing spondylitis aged 相似文献   

Isolation of a Ca2+-releasing factor from caffeine-treated skeletal muscle fibres and its effect on Ca2+ release from sarcoplasmic reticulum

Summary In the presence of 2mm caffeine, skeletal muscles of the frog exert small irregular oscillations of single sarcomeres. A factor, released from these oscillating muscles, was partially purified, and its activity was tested on skinned fibres and isolated vesicles of the sarcoplasmic reticulum (SR). Purification was achieved in three steps by gel filtration and reversed phase chromatography, and the active compound of the released material was shown probably to be a small peptide. In skinned fibres, the purified factor evoked repetitive contractions and subthreshold sarcomeric oscillations. In heavy SR vesicles passively loaded with⁴⁵Ca²⁺, the factor induced a small but significant increase in the⁴⁵Ca²⁺ efflux rate. At the single channel level, the open probability of the SR Ca²⁺ release channel increased when the factor was added to the cytoplasmic side of the channel. The results reveal that the released factor potentiates Ca²⁺ release from the SR by increasing the open time of the Ca²⁺ release channel.     

Highly efficient antigen targeting to M-DC8+ dendritic cells via FcgammaRIII/CD16-specific antibody conjugates

Conjugates of peptide antigens with antibodies specifically recognizing surface molecules on dendritic cells (DC) represent an attractive approach to target antigens to antigen-presenting cells (APC) for the induction of specific T cell responses. The present study evaluates the potential of M-DC8(+) DC, a sub-population of professional APC in the blood, for an antibody-based vaccination strategy. We prepared, by chemical cross-linking, conjugates of peptide model antigens with antibodies directed against different cell surface molecules of DC. Antigen-peptide conjugates using an anti-CD16 (FcgammaRIII) antibody were most potent in inducing in vitro activation of a specific CD4(+) T cell response. They were at least 300 times more efficient than two other antibody-antigen conjugates and approximately 500 times more efficient than unconjugated antigen peptides. Our data demonstrate that specific antigen targeting via CD16 on M-DC8(+) DC is a promising vaccination approach for the efficient induction of specific CD4(+) T cell responses ex vivo, and perhaps in vivo.     

Identification of 36 novel Jagged1 (JAG1) mutations in patients with Alagille syndrome

Alagille syndrome (AGS) is an autosomal dominant disorder characterized by five major symptoms: cholestasis, vertebral deformity, heart malformations, ocular defects and peculiar facial appearance. The previously described Jagged1 (JAG1) gene on chromosome 20p12 has been identified as being responsible for AGS. JAG1 encodes a transmembrane protein acting as ligand for the evolutionarily conserved Notch signaling pathway. Here we report 36 novel mutations in the JAG1 gene. We identified 12 novel deletions, 4 insertions, 8 missense, 7 nonsense and 5 splice site mutations. All mutations map to the sequence encoding the extracellular part of the Jagged1 protein. The mutations spread over the entire gene with slightly increased rates in exons 2 to 6 and exon 23 and 24. Eight novel missense mutations map to the Delta-Serrate-Lag2 (DSL) domain and adjacent sequences which are important for ligand-receptor interaction. Inheritance was determined in 27 families. Sixteen mutations (55%) were de novo and eleven mutations (45%) were transmitted. Altogether 226 different JAG1 mutations have been described in association with AGS, including our novel 36 mutations. AGS variants are spread over the entire gene with only a few mutations in exon 26. A relatively high number of mutations are clustered in exons 2 to 6. This sequence region shows high interspecies conservation and encodes the Notch receptor-binding region (DSL domain).     

Laser microdissection of small tissue samples--application to chronic pancreatitis tissues

Laser microdissection is considered to be the gold standard of tissue sampling, especially if a defined small tissue area consisting of single or few cells within a heterogeneous tissue compartment is of interest. This sophisticated technique offers the opportunity of rapid and contamination-free tissue sampling for RNA- or DNA-based molecular genetic studies. We have applied laser microdissection to a molecular genetic study of pancreatic intraductal lesions (PanINs) in tissues of chronic pancreatitis, where an exact microdissection of small ducts within a dense fibrous tissue is of paramount importance for following analysis. From nine patients suffering from chronic pancreatitis, formalin-fixed, paraffin-embedded tissue specimens were laser microdissected, and a total of 202 normal ducts and PanINs of grade PanIN-1A to grade PanIN-2 were harvested. After whole genome amplification by improved primer extension and preamplification PCR (I-PEP-PCR), microsatellite-PCR based loss of heterozygosity analysis (LOH) of the tumor suppressor gene loci TP53, p16INK4, and DPC4 was performed. One of 85 informative duct lesions (1.2%) had LOH of TP53, 1 of 76 duct lesions (1.3%) had LOH of DPC4, and 2/29 duct lesions (6.9%) showed LOH of p16INK4. Microsatellite instability (MSI) was seen in 2 of 178 duct lesions (1.1%). Immunohistochemical staining of p53 protein and DPC4 protein revealed no aberrant expression. These preliminary data indicate that LOH of tumor suppressor genes, important in pancreatic cancer genesis or MSI, can be found in chronic pancreatitis tissues, but their incidence is low.     

Progressive systemische Sklerodermie Behandlungsergebnisse unter extrakorporaler Photopherese Behandlungsergebnisse unter extrakorporaler Photopherese

Die Behandlung der progressiven systemischen Sklerodermie (PSS) ist noch nicht befriedigend. Wir berichten in einer nichtrandomisierten, nichtkontrollierten Studie über klinische, laborchemische und immunologische Befunde im Verlauf der extrakorporalen Photopherese (ECP) über 8 Zyklen bei 26 Patienten mit PSS (6 M?nner und 20 Frauen). Die Therapie erfolgte an zwei aufeinanderfolgenden Tagen einmal monatlich. Die 8-Methoxypsoralen-Spiegel wurden mittels HPLC in Plasma und „buffy coat” kontrolliert. Neben einem standardisierten Untersuchungsprogramm wurden Bestimmungen von Entzündungs- und Immunparametern vorgenommen. In der globalen Bewertung durch den Arzt wurde bei 18 Patienten eine partielle Remission, bei 8 eine Stabilisierung der Erkrankung und in einem Fall eine geringgradige Progression festgestellt. Im peripheren Blutbild konnte eine signifikante Zunahme von CD3-positiven NK-Zellen (p=0,03) bei Abnahme der Leukozytenzahl von 2255,4 auf 1156,2 Zellen/μl beobachtet werden. Es kam zu einer nichtsignifikanten Abnahme der Elastase (102,9 vs 90,4 ng/ml), der Sulfidoleukotriene (2255,4 vs. 1688,9 pg/ml), von ICAM-1 (301,9 vs. 276,6 ng/ml), l?slichem IL-2-Rezeptor (609,0 vs. 422,3 U/ml) und IL-10 (164,7 vs. 138,7 pg/ml). IL-6 und IL-8 zeigten keine signifikanten Ver?nderungen. Die ECP-Therapie scheint immunmodulierende Effekte zu haben, wie Entzündungsparameter und zirkulierende Zytokin-Spiegel verdeutlichen. Bereits nach 8 Zyklen war eine partielle Remission und oder Stabilisierung des Krankheitsverlaufes in der globalen Bewertung sowie anhand einzelner klinischer Symptome festzustellen. Zu den langzeitigen Effekten der ECP fehlen bislang ausreichende Daten.