Pediatric medulloblastoma express immune checkpoint B7-H3.

PURPOSE: Medulloblastomas (MB) are highly malignant brain tumors that predominantly occur in young infants. Immunotherapy to boost the immune system is emerging as a novel promising approach, but is often hampered by inhibitory immune checkpoints. In the present study, we have studied immune checkpoint B7-H3 expression in a tissue cohort of human pediatric MB. METHODS: Expression of B7-H3 was detected by immunohistochemistry and classified via B7-H3 staining intensity and percentage of B7-H3 positive tumor cells. Subsequently, B7-H3 protein expression was distinguished in MB molecular subtypes and correlated to immune cell infiltrates, patient characteristics, and survival. RESULTS: B7-H3 protein expression was found in 23 out of 24 (96%) human pediatric MB cases and in 17 out of 24 (71%) MB cases > 25% of tumor cells had any level of B7-H3 expression. B7-H3 protein expression was more frequent on Group-4 MB as compared with other molecular subtypes (p = 0.02). Tumors with high B7-H3 expression showed less influx of γδT cells (p = 0.002) and CD3+ T cells (p = 0.041). CONCLUSION: Immune checkpoint B7-H3 is differentially expressed by the large majority of pediatric MB. This further warrants the development of novel B7-H3-directed (immuno)therapeutic methods for children with incurable, metastatic, or chemo-resistant MB.

Metformin protects from oxaliplatin induced peripheral neuropathy in rats.

Oxaliplatin is a commonly used drug to treat cancer, extending the rate of disease-free survival by 20% in colorectal cancer. However, oxaliplatin induces a disabling form of neuropathy resulting in more than 60% of patients having to reduce or discontinue oxaliplatin, negatively impacting their chance of survival. Oxaliplatin-induced neuropathies are accompanied by degeneration of sensory fibers in the epidermis and hyperexcitability of sensory neurons. These morphological and functional changes have been associated with sensory symptoms such as dysesthesia, paresthesia and mechanical and cold allodynia. Various strategies have been proposed to prevent or treat oxaliplatin-induced neuropathies without success. The anti-diabetic drug metformin has been recently shown to exert neuroprotection in other chemotherapy-induced neuropathies, so here we aimed to test if metformin can prevent the development of oxaliplatin-induced neuropathy in a rat model of this condition. Animals treated with oxaliplatin developed significant intraepidermal fiber degeneration, a mild gliosis in the spinal cord, and mechanical and cold hyperalgesia. The concomitant use of metformin prevented degeneration of intraepidermal fibers, gliosis, and the altered sensitivity. Our evidence further supports metformin as a new approach to prevent oxaliplatin-induced neuropathy with a potential important clinical impact.

The Co-Expression of Kallikrein 5 and Kallikrein 7 Associates with Poor Survival in Non-HPV Oral Squamous-Cell Carcinoma.

OBJECTIVE: Oral squamous-cell carcinoma (OSCC) still has a poor prognosis. Lymph node metastasis (LNM) is a major determinant of treatment decisions and prognosis. Serine protease inhibitor Kazal-type 5 (SPINK5) is the inhibitor of kallikrein 5 (KLK5) and KLK7. SPINK5, KLK5 and KLK7 are three of the genes of a recently validated LNM-predicting gene expression profile in OSCC. This study evaluates their clinicopathological role and value as biomarkers in OSCC. METHODS: Eighty-three patients with primary OSCC, treated surgically between 1996 and 2000, were included. Gene expression data were acquired from a previously reported study. Human papillomavirus (HPV) status was determined by an algorithm for HPV-16. Protein expression for KLK5, KLK7 and SPINK5 was semi-quantitatively determined in all 83 tumours by immunohistochemistry. All expression data were correlated with clinicopathological parameters. RESULTS: Concurrent loss of KLK5 and KLK7 correlates with worse disease-specific and overall survival (DSS and OS). Multivariate analysis proved that co-expression is an independent prognostic factor for DSS (p = 0.029) and OS (p = 0.001). CONCLUSION: This report demonstrates that concurrent loss of KLK5 and KLK7 associates with a poor clinical outcome in OSCC and could therefore serve as prognostic marker in this disease.

Methylation specific PCR to characterize methylation of the promoter of deoxycytidine kinase.

Deoxycytidine kinase (dCK) is essential for phosphorylation of natural deoxynucleosides and analogs, such as gemcitabine and cytarabine, two widely used anticancer compounds. We hypothesized that DNA methylation of SP1 binding sites in the dCK promoter region might affect dCK expression. Using methylation specific PCR (MSP), methylation was detected in one of the SP1 binding sites of the dCK promoter, in most tested cancer cell lines and in patient samples from brain tumors and leukemia. This SP1 site is a 3'GC box, which upon hypomethylation negatively regulates dCK mRNA expression. In conclusion, we developed a new MSP method showing methylation of the 3' GC-box in the dCK promoter region in tumor cells and patient samples. Methylation might therefore regulate transcription of dCK, and should be studied further to understand its role in influencing gemcitabine and cytarabine activity.

Ectopic expression of the serine protease inhibitor PI9 modulates death receptor-mediated apoptosis.

Apoptosis is a highly controlled process, whose triggering is associated with the activation of caspases. Apoptosis can be induced via a subgroup of the tumor necrosis factor (TNF) receptor superfamily, which recruit and activate pro-caspase-8 and -10. Regulation of apoptosis is achieved by several inhibitors, including c-FLICE-inhibitory protein, which prevents apoptosis by inhibiting the pro-apoptotic activation of upstream caspases. Here we show that the human intracellular serine protease inhibitor (serpin), protease inhibitor 9 (PI9), inhibits TNF-, TNF-related apoptosis-inducing ligand- and Fas ligand-mediated apoptosis in certain TNF-sensitive cell lines. The reactive center P1 residue of PI9 was required for this inhibition since PI9 harboring a Glu --> Ala mutation in its reactive center failed to impair death receptor-induced cell death. This suggests a classical serpin-protease interaction. Indeed, PI9 inhibited apoptotic death by directly interacting with the intermediate active forms of caspase-8 and -10. This indicates that PI9 can regulate pro-apoptotic apical caspases.

Peroxisome proliferator-activated receptor expression is reduced in skeletal muscle in COPD.

Chronic obstructive pulmonary disease (COPD) is a multiorgan systemic disease. The systemic features are skeletal muscle weakness and cachexia, the latter being associated with systemic inflammation. The exact mechanisms underlying skeletal muscle dysfunction in COPD remain obscure. Recent evidence suggests involvement of the peroxisome proliferator-activated receptors (PPARs) and PPAR-gamma coactivator (PGC)-1alpha in regulation of skeletal muscle morphology and metabolism, and mitochondrial transcription factor A (TFAM) has been implicated in the process of mitochondrial biogenesis. The aim of the present exploratory study was, therefore, to compare these factors in the skeletal muscle of nine healthy control subjects and 14 COPD patients stratified by cachexia. PPAR-gamma, PPAR-delta and TFAM were measured at the mRNA and protein level by real-time quantitative PCR and Western blotting, respectively. PPAR-alpha and PGC-1alpha were meansured at the mRNA level. PPAR-delta and TFAM protein content, as well as PGC-1alpha mRNA levels, were decreased in the skeletal muscle of COPD patients compared with healthy controls. The cachectic COPD subgroup was further characterised by decreased PPAR-alpha mRNA expression and decreased TFAM protein and mRNA levels compared with noncachectic COPD patients. In addition, PPAR-alpha mRNA levels in skeletal muscle correlated negatively with inflammatory markers in plasma. Therefore, a disturbed expression of these regulatory factors may well underlie the disturbed skeletal muscle functioning in chronic obstructive pulmonary disease.

Raised CRP levels mark metabolic and functional impairment in advanced COPD.

BACKGROUND: C-reactive protein (CRP) is often used as a clinical marker of acute systemic inflammation. Since low grade inflammation is evident in chronic diseases such as chronic obstructive pulmonary disease (COPD), new methods have been developed to enhance the sensitivity of CRP assays in the lower range. A study was undertaken to investigate the discriminative value of high sensitivity CRP in COPD with respect to markers of local and systemic impairment, disability, and handicap. METHODS: Plasma CRP levels, interleukin 6 (IL-6) levels, body composition, resting energy expenditure (REE), exercise capacity, health status, and lung function were determined in 102 patients with clinically stable COPD (GOLD stage II-IV). The cut off point for normal versus raised CRP levels was 4.21 mg/l. RESULTS: CRP levels were raised in 48 of 102 patients. In these patients, IL-6 (p<0.001) and REE (adjusted for fat-free mass, p = 0.002) were higher while maximal (p = 0.040) and submaximal exercise capacity (p = 0.017) and 6 minute walking distance (p = 0.014) were lower. The SGRQ symptom score (p = 0.003) was lower in patients with raised CRP levels, as were post-bronchodilator FEV1 (p = 0.031) and reversibility (p = 0.001). Regression analysis also showed that, when adjusted for FEV1, age and sex, CRP was a significant predictor for body mass index (p = 0.044) and fat mass index (p = 0.016). CONCLUSIONS: High sensitivity CRP is a marker for impaired energy metabolism, functional capacity, and distress due to respiratory symptoms in COPD.

The human equilibrative nucleoside transporter 1 mediates in vitro cytarabine sensitivity in childhood acute myeloid leukaemia.

Cytarabine (ara-C) is the most effective agent for the treatment of acute myeloid leukaemia (AML). Aberrant expression of enzymes involved in the transport/metabolism of ara-C could explain drug resistance. We determined mRNA expression of these factors using quantitative-real-time-PCR in leukemic blasts from children diagnosed with de novo AML. Expression of the inactivating enzyme pyrimidine nucleotidase-I (PN-I) was 1.8-fold lower in FAB-M5 as compared to FAB-M1/2 (P=0.007). In vitro sensitivity to deoxynucleoside analogues was determined using the MTT-assay. Human equilibrative nucleoside transporter-1 (hENT1) mRNA expression and ara-C sensitivity were significantly correlated (rp=-0.46; P=0.001), with three-fold lower hENT1 mRNA levels in resistant patients (P=0.003). hENT1 mRNA expression also seemed to correlate inversely with the LC50 values of cladribine (rp=-0.30; P=0.04), decitabine (rp=-0.29; P=0.04) and gemcitabine (rp=-0.33; P=0.02). Deoxycytidine kinase (dCK) and cytidine deaminase (CDA) mRNA expression seemed to correlate with in vitro sensitivity to gemcitabine (rp=-0.31; P=0.03) and decitabine (rp=0.33; P=0.03), respectively. The dCK/PN-I ratio correlated inversely with LC50 values for gemcitabine (rp=-0.45, P=0.001) and the dCK/CDA ratio seemed to correlate with LC50 values for decitabine (rp=-0.29; 0.04). In conclusion, decreased expression of hENT1, which transports ara-C across the cell membrane, appears to be a major factor in ara-C resistance in childhood AML.

Polyunsaturated fatty acids improve exercise capacity in chronic obstructive pulmonary disease.

BACKGROUND: Muscle wasting and decreased muscle oxidative capacity commonly occur in patients with chronic obstructive pulmonary disease (COPD). Polyunsaturated fatty acids (PUFA) have been shown to mediate several inflammatory and metabolic pathways which may be involved in the pathogenesis of muscle impairment in COPD. The aim of this study was to investigate the effect of PUFA modulation on systemic inflammation, reversal of muscle wasting, and functional status in COPD. METHODS: Eighty patients with COPD (57 men) with forced expiratory volume in 1 second (FEV1) 37.3 (13.8)% predicted received 9 g PUFA or placebo daily in a double blind randomised fashion during an 8 week rehabilitation programme. Body composition (bioelectrical impedance), functional capacity (lung function, incremental cycle ergometry test, submaximal cycle test, isokinetic quadriceps strength) and inflammatory markers (C-reactive protein (CRP), interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha) were assessed at baseline and after 8 weeks. RESULTS: Both groups had similar increases in weight, fat-free mass (FFM), and muscle strength. The peak load of the incremental exercise test increased more in the PUFA group than in the placebo group (difference in increase 9.7 W (95% CI 2.5 to 17.0), p = 0.009) even after adjustment for FFM. The duration of the constant work rate test also increased more in patients receiving PUFA (difference in increase 4.3 min (95% CI 0.6 to 7.9), p = 0.023). The positive effects of PUFA could not be attributed to a decrease in systemic levels of CRP, IL-6 and TNF-alpha. CONCLUSIONS: This is the first study to show beneficial effects of PUFA on exercise capacity in patients with COPD.

Leptin as local inflammatory marker in COPD.

INTRODUCTION: Chronic inflammation of the lung is a characteristic finding in chronic obstructive pulmonary disease (COPD). Leptin is a pleiotropic cytokine thought to play a role in host response to inflammation. As recent studies have shown that leptin receptors are present in the lung, this study aimed to determine if leptin is detectable in induced sputum of COPD patients and if there is a relationship between leptin and other inflammatory markers in sputum. METHODS: Sputum was induced in 14 male patients with moderate COPD (FEV1: 56 (15) % pred.). Leptin, total tumour necrosis factor (TNF)-alpha, and C-reactive protein (CRP) were analyzed in induced sputum supernatant by ELISA. Leptin was also determined in EDTA plasma. RESULTS: Leptin was detectable in induced sputum of 10 COPD patients. A significant relationship was found between sputum leptin and CRP (r = 0.943, P < 0.001) and total TNF-alpha (r = 0.690, P < 0.01). Plasma leptin and sputum leptin were inversely correlated (r = -0.643, P < 0.01). CONCLUSION: The present study demonstrated that leptin is detectable in induced sputum of patients with moderate COPD and is related to other inflammatory markers. The observed correlations between leptin and inflammatory markers in sputum may indicate that leptin is involved in the local inflammatory response in COPD.

Diverging pathways for lipopolysaccharide and CD14 in human monocytes.

BACKGROUND: CD14 is considered to be the major endotoxin (lipopolysaccharide [LPS]) binding molecule on human monocytes. It initiates cellular response, but its role in the clearance of LPS is not well understood. Under conditions that ensure totally CD14-dependent LPS binding on human monocytes, the internalization mechanisms of LPS and CD14 were studied. METHODS: The uptake and intracellular distribution of fluorescein isothiocyanate (FITC)-LPS and CD14 was determined by flow cytometry, trypan blue quenching, and confocal fluorescence microscopy. Incubation of surface-biotinylated cells with LPS at 37 degrees C or 4 degrees C and subsequent subfractionation was used to further characterize CD14 internalization. The amount of the intracellular CD14 was estimated by CD14 enzyme-linked immunosorbent assay (ELISA). RESULTS: The internalization rate of 10 ng/ml FITC-LPS with 1% human serum was 1% of bound endotoxin per minute, whereas CD14 expression did not decrease at the same time surface. We proved the presence of an intracellular CD14 pool (2.68 x 10(6) molecules per unstimulated monocyte) and could show that internalized FITC-LPS molecules can be found in different intracellular compartments than CD14. Subfractionation of LPS-treated biotinylated monocytes showed no change in biotinylated CD14 in the membrane fraction independently of the incubation temperature (37 degrees C or at 4 degrees C) used, indicating that these CD14 molecules were not taken up by an active process. CONCLUSIONS: These data indicate the presence of a large intracellular CD14 pool in monocytes with a yet unknown function, and suggest that LPS and CD14 molecules can be internalized independently after association on the cell surface.

The effect of unfiltered coffee on potential biomarkers for colonic cancer risk in healthy volunteers: a randomized trial.

BACKGROUND: Epidemiologic studies suggest that coffee use might protect against colorectal cancer. Inconsistencies as to the effect of coffee use and colorectal cancer between epidemiologic studies might be related to the type of coffee brew. OBJECTIVE: We studied the effect of unfiltered coffee consumption on putative biomarkers for colonic cancer risk. DESIGN: A total of 64 healthy volunteers (31 men and 33 women), with a mean age of 43 +/- 11 years were randomly assigned to two groups in a crossover design, with two intervention periods of 2 weeks separated by a washout period of 8 weeks. Treatments were 1 L of cafetière (French press) coffee daily or no coffee. At the end of each intervention period, fasting blood samples, colorectal biopsies and 48 h faeces were collected. RESULTS: No effect of coffee on colorectal cell proliferation, assayed by estimating the Proliferating Cell Nuclear Antigen labelling index, was seen. Additionally, no effects were seen on the concentrations of faecal soluble bile acids and colorectal mucosal glutathione S-transferase activity. However, unfiltered coffee significantly increased the glutathione content in the colorectal mucosa by 8% and in plasma by 15%. Other aminothiols in plasma also increased on coffee. CONCLUSION: Unfiltered coffee does not influence the colorectal mucosal proliferation rate, but might increase the detoxification capacity and anti-mutagenic properties in the colorectal mucosa through an increase in glutathione concentration. Whether this effect indeed contributes to a lower colon cancer risk remains to be established.

Unfiltered coffee increases plasma homocysteine concentrations in healthy volunteers: a randomized trial.

BACKGROUND: An elevated plasma homocysteine concentration is a putative risk factor for cardiovascular disease. Observational studies have reported an association between coffee consumption and plasma homocysteine concentrations. OBJECTIVE: We studied the effect of coffee consumption on plasma homocysteine in a crossover trial. We used unfiltered coffee so as to include the possible effects of coffee diterpenes, which are removed by filtering. DESIGN: Sixty-four healthy volunteers (31 men and 33 women) with a mean (+/-SD) age of 43 +/- 11 y were randomly assigned to 2 groups. One group (n = 30) drank 1 L unfiltered cafetière (French press) coffee daily for 2 wk. Such coffee is rich in the cholesterol-raising diterpenes kahweol and cafestol. The other group (n = 34) received water, milk, broth, tea, and chocolate drinks instead of coffee. After a washout period of 8 wk, both groups received the alternate intervention for another 2 wk. RESULTS: Consumption of 1 L unfiltered coffee/d for 2 wk significantly raised fasting plasma homocysteine concentrations by 10%, from 12.8 to 14.0 micromol/L. CONCLUSIONS: Unfiltered coffee increases plasma homocysteine concentrations in volunteers with normal initial concentrations. It is unclear whether the effect is caused by the cholesterol-raising diterpenes present exclusively in unfiltered coffee or by factors that are also present in filtered coffee.

T cell apoptosis in human heart allografts: association with lack of co-stimulation?

It is unclear whether the intracardial immune reactivity after heart transplantation influences the peripheral immunological status (activation or nonresponsiveness) of the patient. Co-stimulation and activation-induced cell death (AICD) or apoptosis play an important role in determining the balance between lymphocyte reactivity and nonreactivity. Therefore, we studied the expression of co-stimulatory molecules and the process of apoptosis in biopsies of human heart allografts, using immunohistochemistry. Although a normal expression of co-stimulatory molecules on antigen-presenting cells was observed, the expression of their counter-structures on T cells was absent. This may be due to chronic T cell activation, which can lead to the induction of apoptosis via the Fas/Fas ligand pathway. In the infiltrates, a considerable percentage of the lymphocytes, but not the macrophages, were apoptotic. Apoptosis was confirmed by DNA fragmentation analysis. Increased numbers of Bax-expressing versus decreased numbers of Bcl2-expressing lymphocytes in comparison with normal lymphoid tissue confirmed a imbalance in favor of apoptosis. Apoptosis was biased towards CD4+ T cells (65.7% versus 26.6% in CD8+ T cells). Fas was expressed on most of the infiltrating cells. Fas ligand expression was also observed, not only on most of the T cells but also on all macrophages. Because macrophages were often detected in close contact with T cells, they may play a role in T cell regulation via the Fas/Fas ligand pathway. This study indicates that, during rejection, not only is tissue damage induced by infiltrating T cells, but also the infiltrating lymphocytes themselves are actively down-regulated (eg, AICD) by one another and by macrophages in the infiltrate. This regulatory process may affect the immunological status of the patient after heart transplantation.

Immunohistochemical demonstration of cellular antigens of the cat defined by anti-human antibodies.

A panel of monoclonal antibodies (mAb) and some polyclonal rabbit sera directed against human antigens were studied on cryostat tissue sections of three cats using immunohistochemistry. Reactivity of the antibodies was tested on feline tonsil, intestine, thymus, lymph node and spleen with a three-step immunoperoxidase technique and compared with reactions on human thymus, lymph node and spleen. From a total of 95 antibodies, 28 gave reactivity comparable with that in human tissues. The remaining antibodies gave none or miscellaneous results. The positive reactions in the cat included antibodies directed to adhesion molecules (VLA-2 and VLA-4), to natural killer (NK) cells (CD56, CD57 and NCAM), to complement receptor CR1, to proliferation marker Ki-67 (MIB-1), to endothelial antigens (EN-4, PAL-E and von Willebrand factor) and to structural proteins like vimentin, desmin, collagen type IV and cytokeratin. The identification of these cross-reacting antibodies extends the spectrum of immunological reagents that are now available for the cat, and will thus contribute to the study of the feline immune system.

An improved, sensitive, non-radioactive in situ hybridization method for the detection of cytokine mRNAs.

We established an improved non-radioactive in situ hybridization (ISH) method to detect mRNA of cytokines in cell preparations and tissues. Via this method we could demonstrate various cytokines in stimulated peripheral blood mononuclear cells (PBMC), lymphoid cell lines and human lymphoid tissues. The probes for the in situ hybridization were made by labelling cytokine-specific PCR products with digoxigenin (Dig) in a repeated PCR. This resulted in an intrinsic labelling of the probe with several Dig-UTP molecules. Incorporation of Dig-11-dUTPs was shown on ethidium bromide-stained agarose gels by a higher molecular weight of the PCR products with incorporated Dig-dUTPs when compared to control PCR products without digoxigenin. Cytospin-centrifuged cells of PHA-stimulated PBMC or lymphoid cell lines and frozen sections of various human lymphoid tissues were hybridized with the Dig-labelled cytokine probes and the hybridized probes were detected immuno-histochemically. In this way, we detected and localized cytokine mRNAs (IL-2, IL-4, IL-6, IL-8, IL-10) in PBMC, in the human T-cell line Jurkat, in the follicular lymphoma cell line DoHH2, and in human lymph nodes and tonsils. The in situ hybridization had a high sensitivity as the results correlated closely with the detection of cytokine mRNA by reverse transcriptase-PCR (RT-PCR) data from the same samples. We showed that Jurkat and DoHH2 cells produce several cytokines constitutively and that, after activation with the phorbol ester PMA, expression of several cytokine mRNAS was enhanced.

Encoded latent membrane protein 1 of Epstein-Barr virus on follicular dendritic cells in residual germinal centres in Hodgkin's disease.

AIMS: To determine if there is an association between Epstein-Barr virus (EBV) infection and Hodgkin's disease. METHODS: Fifty cases of Hodgkin's disease and 25 reactive lymph nodes were screened for the presence of EBV-RNA (EBER) using in situ hybridisation, and for the expression of EBV encoded latent membrane protein 1 (LMP-1) by immunohistochemistry. RESULTS: In 42% of the cases of Hodgkin's disease, EBER was detected in the nuclei of the malignant cells, and in LMP-1 expression was found 36%. Both EBER and LMP-1 positivity were seen in 34% of the cases. An additional finding was the presence of LMP-1 on follicular dendritic cells in residual germinal centres in two cases of Hodgkin's disease. EBER was not detected in these germinal centres. In reactive lymph nodes only occasional EBER positive, small, lymphoid cells were found, without LMP-1 expression. CONCLUSIONS: These results show a strong correlation between the presence of EBER and the LMP-1 expression in the Reed-Sternberg cells. They corroborate a role for EBV in at least some cases of Hodgkin's disease. LMP-1 is probably presented as an immune complex in the germinal centres, as part of an immune response against EBV.

The neuro-endocrine component of the rat thymus: studies on cultured thymic fragments before and after transplantation in congenitally athymic and euthymic rats.

An immunohistochemical study was done for the presence of tyrosine hydroxylase (noradrenergic innervation), neuron-specific protein PGP9.5, and anterior pituitary hormones (beta-subunit of follicle-stimulating hormone, growth hormone, beta-subunit of luteinizing hormone, prolactin, and beta-subunit of thyroid-stimulating hormone) in cultured thymic fragments before and after transplantation in congenitally athymic and euthymic rats. The cultured thymic fragments consisted of epithelial cells and were depleted of lymphocytes. After implantation in syngeneic and allogeneic athymic recipients and in syngeneic euthymic recipients, a recovery of the original architecture was found within 6 weeks; rejection occurred within 3 weeks for allogeneic transplantation in euthymic rats. During culture nerve-like profiles almost disappeared from the tissue, and reappeared simultaneously with the influx of host-derived cells and the restoration of the original thymic architecture. A high immunoreactivity for hormones and PGP9.5 was found in epithelial cells after culture and in the first phase after transplantation. These epithelial cells may represent precursor-epithelial cells, based on their unusual ultrastructure and combined expression of markers that in the normal thymus occur only on subcapsular/medullary epithelium or on cortex epithelium. These data indicate a potential role of the neuroendocrine function of the thymus during restoration of the thymus architecture starting from precursor-like epithelial cells.

Transplantation of cultured thymic fragments in congenitally athymic and euthymic rats. Culture with deoxyguanosine or cyclosporin A does not influence the histologic characteristics and outcome after transplantation in syngeneic and allogeneic combinations.

Cultured thymic fragments (CTF) from WAG/CPB (RT1u) and DA/01a (RT1a) rats were prepared in the presence or absence of 2'deoxyguanosine or cyclosporin A, and subsequently transplanted under the kidney capsule of congenitally athymic and euthymic WAG/CPB recipients. The rationale of the culture supplements was that these may affect the disappearance of medullary dendritic cells, with subsequent induction of allotolerance. However, the immunohistology of the CTF showed more RT1 class II-positive cells than keratin-positive cells, indicative of the maintenance of dendritic cells. Grafts in athymic animals showed the recovery of the original thymic architecture within 6 weeks after transplantation. The influx of host-derived lymphocytes was accompanied by an influx of dendritic cells in the medulla-like area and macrophages in the cortex. A similar recovery was observed for syngeneic CTF in euthymic recipients. In addition lymphocytic infiltration was seen in the connective tissue surrounding the epithelial areas. Allogeneic grafts in euthymic animals were rejected within 3 weeks after transplantation. This outcome of the transplanted CTF under different conditions was not affected by the supplementation of the thymic culture before transplantation with 2'deoxyguanosine or cyclosporin A. We conclude that there is no tolerance induction after transplantation in euthymic allogeneic rats of CTF prepared in the presence of 2'deoxyguanosine. This conclusion is in contrast to data in the mouse, which may be explained by the maintenance of dendritic cells during culture. A chimaeric state of donor-derived epithelium and host-derived dendritic cells is obtained by transplantation of allografts in athymic rats.