CD74 regulates complexity of tumor cell HLA class II peptidome in brain metastasis and is a positive prognostic marker for patient survival

Despite multidisciplinary local and systemic therapeutic approaches, the prognosis for most patients with brain metastases is still dismal. The role of adaptive and innate anti-tumor response including the Human Leukocyte Antigen (HLA) machinery of antigen presentation is still unclear. We present data on the HLA class II-chaperone molecule CD74 in brain metastases and its impact on the HLA peptidome complexity.We analyzed CD74 and HLA class II expression on tumor cells in a subset of 236 human brain metastases, primary tumors and peripheral metastases of different entities in association with clinical data including overall survival. Additionally, we assessed whole DNA methylome profiles including CD74 promoter methylation and differential methylation in 21 brain metastases. We analyzed the effects of a siRNA mediated CD74 knockdown on HLA-expression and HLA peptidome composition in a brain metastatic melanoma cell line.We observed that CD74 expression on tumor cells is a strong positive prognostic marker in brain metastasis patients and positively associated with tumor-infiltrating T-lymphocytes (TILs). Whole DNA methylome analysis suggested that CD74 tumor cell expression might be regulated epigenetically via CD74 promoter methylation. CD74high and TILhigh tumors displayed a differential DNA methylation pattern with highest enrichment scores for antigen processing and presentation. Furthermore, CD74 knockdown in vitro lead to a reduction of HLA class II peptidome complexity, while HLA class I peptidome remained unaffected.In summary, our results demonstrate that a functional HLA class II processing machinery in brain metastatic tumor cells, reflected by a high expression of CD74 and a complex tumor cell HLA peptidome, seems to be crucial for better patient prognosis.

Notch receptors in human choroid plexus tumors

Notch signaling plays a role in development and formation of the normal choroid plexus (nCP), and in formation of various tumors in humans. Activation of Notch3 has been reported to promote tumor growth in invasive gliomas and to initiate formation of choroid plexus tumors (CPT) in mice. We investigated the expression of all currently known Notch receptors (Notch 1-4) in 55 samples of nCP and 88 CPT, including 61 choroid plexus papillomas (CPP), 22 atypical CPP and 5 choroid plexus carcinomas by immunohistochemistry. Notch expression was semiquantitatively evaluated separately for membranous/cytoplasmic and for nuclear staining. In addition, we examined Her2 expression (EGFR2, Her2/neu, ErbB2, CD340) because of its functional link to Notch signaling. All samples were negative for Notch3. Membranous/cytoplasmic expression of Notch1 (p<0.0001) and Notch4 (p=0.046) was significantly higher, whereas Notch2 expression was significantly lower (p<0.0001) in nCP compared to CPT. Nuclear expression of Notch1, -2 and -4 was significantly higher in CPT compared to nCP (p<0.0001 each). Expression of Notch2 and Notch4 showed a shift from a prevailing membranous/cytoplasmic expression in nCP to a predominant nuclear expression in CPT. Her2 was weakly expressed in 42/84 CPT but only in 2/53 nCP (p=0.0001) and positively correlated with nuclear expression of Notch1, -2 and 4 in CPT. In summary, a shift between membranous/cytoplasmic (non-canonical signaling pathway) and nuclear expression (canonical signaling pathway) of Notch1, -2 and -4 and upregulation of Her2 indicate neoplastic transformation in human CP and may reveal new therapeutic approaches.

Pituicytoma in a patient with Cushing's disease: case report and review of the literature

Pituicytoma is an exceptionally rare low-grade glioma (WHO grade I) of the neurohypophysis and infundibulum. We are reporting the case of a 48-year-old man who presented with severe Cushing's syndrome. Endocrinological evaluation unequivocally confirmed pituitary-dependent Cushing's syndrome (=Cushing's disease). Cranial MR-imaging displayed a conspicuous area in the dorsal and basal pituitary gland and a minimal bulging of the pituitary gland paramedian of the pituitary stalk on the right side. Transsphenoidal inspection revealed a small tumor in the basal and dorsal pituitary gland. Surprisingly, the definite postoperative histopathological diagnosis of the removed tumor was pituicytoma and not pituitary adenoma. Hence, the microadenoma responsible for Cushing's disease was not yet removed and persistent hypercortisolism necessitated transsphenoidal re-operation. During re-operation, hemihypophysectomy was performed on the right side. The non-tumorous specimen of the adeno-hypophysis showed signs of Crooke's hyalinization consistent with Cushing's disease. Undetectable postoperative ACTH- and cortisol levels provided clear evidence that the underlying ACTH-source was successfully removed during re-operation. Coincidence of pituicytoma and pituitary-dependent Cushing's disease has not previously been reported.

Common and uncommon imaging findings in progressive multifocal leukoencephalopathy (PML) with differential diagnostic considerations

OBJECTIVE

To provide a practical review of the spectrum of possible imaging findings in patients with progressive multifocal leukoencephalopathy (PML) and to address differentials.

CONCLUSION

PML manifests with a broad spectrum of imaging features. Besides knowledge of preferential location, extent, temporal course, enhancement, results of functional imaging and clinical setting, recognition of imaging findings reflecting active demyelination may help the clinician in appropriately narrowing down the differential diagnosis.

De novo expression of the hemoglobin scavenger receptor CD163 by activated microglia is not associated with hemorrhages in human brain lesions

The main function of CD163 (hemoglobin scavenger receptor) is to bind the hemoglobin-haptoglobin complex, thereby mediating extravasal hemolysis. However, CD163 also has an antiinflammatory function. After CD163-mediated endocytosis, hemoglobin is catabolized further by hemeoxygenase 1 (HO-1). Previously, we found expression of HO-1 to be restricted to microglia/macrophages at sites of hemorrhages in human traumatic and ischemic brain lesions. We now investigated if CD163 expression is also correlated with hemorrhages in brain lesions. Methods. Autopsy brain tissue from 44 cases with hemorrhagic brain lesions (32 traumatic brain injuries/TBI, 12 intracerebral bleedings/ICB), 56 non-hemorrhagic brain lesions (30 ischemias, 26 hypoxias) and 6 control brains were investigated. The post injury survival times ranged from a few minutes to 60 months. Results. In controls, single perivascular monocytes expressed CD163, but only single CD163+ microglia were found in 3/6 cases. CD163+ cells in the parenchyma (activated microglia/macrophages) increased significantly within 24 hours after trauma and ischemia and within 1-7 days following ICB or hypoxia. Overall, significantly lower and higher levels of parenchymal CD163+ cells occurred in hypoxia and ischemia, respectively. Perivascular CD163+ cells also increased significantly in all pathological conditions. In areas remote from circumscribed brain lesions (TBI, ICB, ischemia), significant changes were only found in ICB and ischemia. Conclusions. De novo expression of CD163 by activated microglia/macrophages and CD163+ infiltrating monocytes are neither restricted to nor predominant in hemorrhagic brain lesions. Thus, the antiinflammatory function of CD163 probably predominates, both in hemorrhagic and non-hemorrhagic brain lesions and points to possible immunomodulatory treatment strategies targeting CD163.

Immunohistochemical analysis of CDX2 expression in normal choroid plexus epithelium and choroid plexus tumors

BACKGROUND

The Wnt and BMP signaling pathways are involved in the morphogenesis of both gastrointestinal and choroid plexus epithelium. In the intestine, Wnt signaling represses the expression of the tumor suppressor gene CDX2 via SOX9, a transcription factor, which is also expressed in the choroid plexus. Recently, an inverse correlation between CDX2 expression and tumor grade, tumor stage and lymph node metastasis in colorectal adenocarcinomas has been reported. Besides intestinal tissues, expression of CDX2 has also been reported in various other epithelial tissues and carcinomas. To date, no data exist on expression of CDX2 in normal and neoplastic choroid plexus epithelium.

AIM

To investigate CDX2 expression in normal and neoplastic choroid plexus.

MATERIALS AND METHODS

Paraffin-embedded samples from 60 normal choroid plexus, including 23 fetal tissue samples and from 65 choroid plexus tumors (47 choroid plexus papillomas WHO grade I, 16 atypical choroid plexus papillomas and 2 choroid plexus carcinomas WHO grade III) were examined by immunohistochemistry. Samples from normal choroid plexus were collected from 45 autopsy cases and from 15 neurosurgical specimens.

RESULTS

Normal and neoplastic choroid plexus lacked CDX2 expression.

CONCLUSION

In our series, immunohistochemistry shows no evidence for a role of CDX2 in development or differentiation of normal choroid plexus from the 9th gestational week until adulthood. Since choroid plexus tumors reliably lack CDX2 immunoreactivity, this marker may be helpful in distinguishing cerebral metastases from CDX2-positive adenocarcinomas and choroid plexus neoplasms.

Outcome of transanal endorectal pull-through in patients with Hirschsprung's disease

INTRODUCTION

Various outcomes following transanal endorectal pull-through (TERPT) in patients with Hirschsprung's disease (HD) have been reported. In this study, the postoperative course and functional outcome after TERPT in 25 patients with HD is evaluated.

METHODS

Patient records of children who underwent TERPT for HD between 2002 and 2007 were reviewed retrospectively. Age at surgery, sex, associated malformations, length of follow-up, presence of colostomy, indication for laparotomy, length of the aganglionic segment, result of rectal examination under general anaesthesia 6 weeks after surgery, necessity of a dilatation program or reoperation were investigated. In addition, standardised interviews were performed to collect the following data: bowel movement per day, faecal continence in potty-trained children or in patients older than 3 years, incidence of diarrhoea or problems with micturition and the necessity for laxative therapy.

RESULTS

Between 2002 and 2007, 25 patients underwent TERPT for HD. Median age at the time of surgery was 3.5 months. Median follow-up was 35 months. Calibration of the anus showed a normal age-related diameter of the anus in 12/20 children and a markedly reduced diameter in 8/20 children at 6 weeks postoperatively. Seven of the latter children underwent a dilatation program. A redo pull-through procedure was performed in 3 patients due to stenosis at the colo-anal anastomosis (n=1), a constricting muscle cuff (n=1) and a twisted pull-through (n=1). Two children developed enterocolitis. The median frequency of bowel movements was 3/day (1-5/day). Laxative treatment was required in only one patient (4.5%). None of the patients had diarrhoea. Nineteen children (86%) were potty-trained, being older than 3 years. Eighteen of them were continent (95%). One patient (5%) with trisomy 21 suffered from intermittent non-retentive faecal incontinence. None of the patients showed signs of neurogenic bladder dysfunction.

CONCLUSION

The functional outcome in most patients after TERPT is satisfactory. We suggest that routine rectal digital examination and anal calibration under anaesthesia 6 weeks postoperatively might detect occult anodermal stenosis and allow early initiation of an anorectal dilatation program, which could decrease the incidence of enterocolitis, persistent constipation and the necessity for further surgical intervention.

No evidence for WT1 involvement in a beta-catenin-independent activation of the Wnt signaling pathway in pituitary adenomas

The overexpression of Wilms' tumor gene product WT1, which acts as a tumor suppressor or oncogene, has been reported in various malignancies. Recent studies have shown that the interaction partner Wnt-4 is upregulated in pituitary adenomas dependent on the Pit-1 lineage (somatotrophs, lactotrophs, and thyrotrophs). However, no data on WT1 expression in nontumorous pituitary tissue or pituitary adenomas is available to date. We investigated WT1 expression in 90 paraffin-embedded pituitary adenomas, including eight atypical adenomas, and in 28 nontumorous pituitary glands by immunohistochemistry. WT1 is absent in epithelial cells of all nontumorous pituitary glands and in 87 out of 90 pituitary adenomas. Only two GHomas (including one atypical adenoma) and one gonadotropin-producing adenoma expressed WT1 in the cytoplasm of single tumor cells without nuclear staining. There is no evidence that WT1 does regulate the Wnt-4/beta-catenin-independent pathway which is activated in the Pit-1-expressing subset of pituitary adenomas.

Diagnostic value of WT1 in neuroepithelial tumours

AIMS

Currently, clinical trials using WT1 (Wilms tumour gene) peptide vaccines are conducted in haematopoietic malignancies and solid cancers. Single reports showed that the Wilms tumour gene product WT1 is also expressed in astrocytic neoplasms. Our aim was to investigate WT1 expression in a large cohort of various neuroepithelial tumours of different World Health Organization (WHO) grades and in normal central nervous system (CNS) tissue specimens to test its potential value as a diagnostic marker.

METHODS

Specimens were assessed by RT-PCR, Western blotting and immunohistochemistry. The samples investigated in our study consisted of 334 human neuroepithelial tumours, among those 33 oligodendrogliomas, 219 astrocytomas (including 105 glioblastomas) and 47 ependymomas.

RESULTS

Our results showed a de novo WT1 expression in neuroepithelial tumours. In diffuse astrocytomas and ependymomas, WT1 expression increased significantly with the grade of malignancy. In contrast, no significant difference was seen between WHO grade-II and -III oligodendrogliomas. Controlling for WHO grade, the comparison of oligodendrogliomas with ependymal and astrocytic tumours showed higher expression values for the latter.

CONCLUSIONS

Our study shows that WT1 is expressed de novo in numerous neuroepithelial tumours and increases with the grade of malignancy. These results suggest an important role of WT1 in tumourigenesis and progression in human brain tumours.

Two functionally linked amino acids in the stem 2 region of measles virus haemagglutinin determine infectivity and virulence in the rodent central nervous system

Rodent brain-adapted measles virus (MV) strains, such as CAM/RB and recombinant MVs based on the Edmonston strain containing the haemagglutinin (H) of CAM/RB, cause acute encephalitis after intracerebral infection of newborn rodents. We have demonstrated that rodent neurovirulence is modulated by two mutations at amino acid positions 195 and 200 in the H protein, one of these positions (200) being a potential glycosylation site. In order to analyse the effects of specific amino acids at these positions, we introduced a range of individual and combined mutations into the open reading frame of the H gene to generate a number of eukaryotic expression plasmids. The functionality of the mutant H proteins was assessed in transfected cells and by generating recombinant viruses. Interestingly, viruses caused acute encephalitis only if the amino acid Ser at position 200 was coupled with Gly at position 195, whereas viruses with single or combined mutations at these positions, including glycosylation at position 200, were attenuated. Neurovirulence was associated with virus spread and induction of neuronal apoptosis, whereas attenuated viruses failed to infect brain cells. Similar results were obtained by using primary brain-cell cultures. Our findings indicate that a structural alteration in the stem 2 region of the H protein at position 195 or 200 interferes with infectivity of rodent neurons, and suggest that the interaction of the viral attachment protein with cellular receptors on neurons is affected.

Reactive astrocytes and activated microglial cells express EAAT1, but not EAAT2, reflecting a neuroprotective potential following ischaemia

AIMS

Glutamate receptor antagonists have failed clinical stroke trials and it has been proposed that the action of N-methyl D-aspartate receptors is necessary for neuronal survival. Thus, excitatory amino acid transporters (EAATs) might be a promising therapeutic target. The aim of this study was to investigate glial expression of EAATs following ischaemia.

METHODS AND RESULTS

Expression of EAAT1 (GLAST) and EAAT2 (Glt-1) in 24 cases of ischaemia was examined by immunohistochemistry. Cortical expression of both EAATs in the lesion decreased within 24 h (P < 0.01, each). Whereas EAAT1+ white matter cells increased 18-fold (P < 0.05) within 24 h in the lesion and remained elevated for months in adjacent (469-fold, P < 0.01) and remote areas (20-fold, P < 0.05), EAAT2+ white matter cells were equivalent in ischaemia and controls. In the first week after stroke mainly activated (ramified and amoeboid) microglia expressed EAAT1, whereas monocytic cells in perivascular spaces and foamy macrophages lacked EAAT1. After more than 1 week, predominantly reactive astrocytes expressed EAAT1.

CONCLUSIONS

Microglial EAAT1 expression is restricted to the early/intermediate stage of activation and blood-derived (perivascular) monocytes do not contribute to EAAT1+ cells following ischaemia. Whether a pharmacological increase in glial EAAT expression may compensate for loss of cortical EAAT expression and reduce neuronal damage following stroke requires investigation by further functional studies.

Expression of EAAT1 reflects a possible neuroprotective function of reactive astrocytes and activated microglia following human traumatic brain injury

Glutamate-mediated excitotoxicity is known to cause secondary brain damage following stroke and traumatic brain injury (TBI). However, clinical trials using NMDA antagonists failed. Thus, glial excitatory amino acid transporters (EAATs) might be a promising target for therapeutic intervention.

METHODS AND RESULTS

We examined expression of EAAT1 (GLAST) and EAAT2 (Glt-1) in 36 TBI cases by immunohistochemistry. Cortical expression of both EAATs decreased rapidly and widespread throughout the brain (in lesional, adjacent and remote areas) following TBI. In the white matter numbers of EAAT1+ parenchymal cells increased 39-fold within 24h (p<0.001) and remained markedly elevated till later stages in the lesion (90-fold, p<0.01) and in peri-lesional regions (86-fold, p<0.01). In contrast, EAAT2+ parenchymal cells and EAAT1+ or EAAT2+ perivascular cells did not increase significantly. Within the first days following TBI mainly activated microglia and thereafter mainly reactive astrocytes expressed EAAT1. Perivascular monocytes and foamy macrophages lacked EAAT1 immunoreactivity. We conclude that following TBI i) loss of cortical EAATs contributes to secondary brain damage, ii) glial EAAT1 expression reflects a potential neuroprotective function of microglia and astrocytes, iii) microglial EAAT1 expression is restricted to an early stage of activation, iv) blood-derived monocytes do not express EAAT1 and v) pharmacological modification of glial EAAT expression might further limit neuronal damage.

Fronto-laterally located supratentorial bronchogenic cyst: case report and review of the literature

Bronchogenic cysts are rare findings within the central nervous system and even extremely seldom if they are located supratentorially. We report on a 25-year-old man who presented with a single generalized seizure without any accompanying neurological deficit 6 weeks prior to admission. MRI showed a smoothly limited, non-calcified cyst of a maximum of 55 mm in diameter. Large parts of the membrane were removed through a right anterior craniotomy, and a fenestration into the subarachnoidal space was performed. Histopathological examinations revealed a bronchogenic cyst. Previous reports of neurenteric cysts are reviewed. Therapeutic options, pathogenesis and categorization of this uncommon congenital entity are discussed.

Atypical teratoid-rhabdoid tumor spreading along the trigeminal nerve

We here describe the case of a boy with an atypical teratoid-rhabdoid tumor (ATRT) of the 4th ventricle at 1 year of age and a local tumor recurrence at 19 months of age. Due to brainstem infiltration, only incomplete tumor resection was possible each time. High-dose chemotherapy, stem cell transplantation and irradiation resulted in complete tumor remission on a control MRI. At 8 years of age, another tumor appeared extending from the cerebellopontine angle along the right trigeminal nerve through Meckel's cave into the cavernous sinus. The trigeminal tumor was not in continuity with the primary ATRT but was located within the field of prior irradiation, neuroradiologically mimicking a schwannoma or a meningioma. The origin of the trigeminal tumor as a late metastasis of the former ATRT or as a less likely irradiation-induced secondary ATRT and the operative approach are discussed.

Rosai-Dorfman disease involving the cranial base, paranasal sinuses and spinal cord

Rosai-Dorfman disease is a lymphoproliferative disease that rarely involves the central nervous system. A 32-year-old patient with an extensive process involving the petroclival region, cavernous sinuses, suprasellar region, anterior cranial fossa, paranasal sinuses, nasal cavity and spinal cord is reported. Sinus histiocytosis with massive lymphadenopathy lesions may be dural-based and located in the skull base. As these lesions may clinically and radiologically mimic meningiomas as well as other disorders, Rosai-Dorfman disease should be included in the differential diagnosis of extensive lesions involving the intracranial and spinal compartments along with meningiomatosis and inflammatory diseases. The individual management of Rosai-Dorfman disease may be challenging due to diffuse involvement of neurovascular structures at the skull base.

Expression and functional activity of osteoprotegerin in human malignant gliomas

Apo2L/TRAIL-based therapy is a promising experimental approach to the treatment of human malignant gliomas. Osteoprotegerin (OPG) is a soluble decoy receptor for Apo2L/TRAIL that antagonizes Apo2L/TRAIL-induced apoptosis. High levels of OPG expressed by tumor cells might therefore abrogate the activity of exogenously added or adenovirally expessed Apo2L/TRAIL. Here we assessed the expression of OPG in human gliomas in vivo, in primary glioma cell cultures and in established glioma cell lines. Immunohistochemistry revealed weak OPG immunoreactivity in up to 5% of the tumor cells in 8 of 13 glioblastomas. Strong OPG labeling was detected in single scattered tumor cells in one of these specimens. Five glioblastomas did not express OPG. High OPG expression was found in 1 of 6 primary glioma cell cultures and in 1 of 12 established glioma cell lines, T98G. OPG released by T98G cells was biologically active in that it inhibited Apo2L/TRAIL-induced apoptosis in sensitive glioma cells. Altogether, however, these data suggest that OPG expression may not be a major pathway of glioma cell resistance to future Apo2L/TRAIL-based therapeutic approaches.

Recombinant measles viruses expressing altered hemagglutinin (H) genes: functional separation of mutations determining H antibody escape from neurovirulence

Measles virus (MV) strain CAM/RB, which was adapted to growth in the brain of newborn rodents, is highly neurovirulent. It has been reported earlier that experimentally selected virus variants escaping from the monoclonal antibodies (MAbs) Nc32 and L77 to hemagglutinin (H) preserved their neurovirulence, whereas mutants escaping MAbs K71 and K29 were found to be strongly attenuated (U. G. Liebert et al., J. Virol. 68:1486-1493, 1994). To investigate the molecular basis of these findings, we have generated a panel of recombinant MVs expressing the H protein from CAM/RB and introduced the amino acid substitutions thought to be responsible for antibody escape and/or neurovirulence. Using these recombinant viruses, we identified the amino acid changes conferring escape from the MAbs L77 (377R-->Q and 378M-->K), Nc32 (388G-->S), K71 (492E-->K and 550S-->P), and K29 (535E-->G). When the corresponding recombinant viruses were tested in brains of newborn rodents, we found that the mutations mediating antibody escape did not confer differential neurovirulence. In contrast, however, replacement of two different amino acids, at positions 195G-->R and 200S-->N, which had been described for the escape mutant set, caused the change in neurovirulence. Thus, antibody escape and neurovirulence appear not to be associated with the same structural alterations of the MV H protein.

Differential cellular accumulation of connective tissue growth factor defines a subset of reactive astrocytes, invading fibroblasts, and endothelial cells following central nervous system injury in rats and humans

In brain injury, the primary trauma is followed by a cascade of cellular and molecular mechanisms resulting in secondary injury and scar formation. Astrogliosis and expression of transforming growth factor beta (TGF-beta) are key components of scar formation. A cytokine mediating the effects of TGF-beta is connective tissue growth factor (CTGF), a fibrogenic peptide encoded by an immediate early gene with suggested roles in tissue regeneration and aberrant deposition of extracellular matrix. In order to investigate CTGF in traumatic lesions, we evaluated 20 human brains with traumatic brain injury (TBI) and 18 rat brains with stab wound injury. Compared to remote areas and unaltered control brains, CTGF+ cells accumulated in border zones of the traumatic lesion site (p < 0.0001). In the direct peri-lesional rim, CTGF expression was confined to invading vimentin+, GFAP- fibroblastoid cells, endothelial and smooth muscle cells of laminin+ vessels, and GFAP+ reactive astrocytes. In the direct peri-lesional rim, CTGF+ astrocytes (>80%) co-expressed the activation associated intermediate filaments nestin and vimentin. In injured rat brains, numbers of CTGF+ cells peaked at day 3 and 7 and decreased to almost base level 3 weeks postinjury, whereas in humans, CTGF+ cells remained persistently elevated up to 6 months (p < 0.0001). The restricted accumulation of CTGF+-reactive astrocytes and CTGF+ fibroblastoid cells lining the adjacent laminin+ basal lamina suggests participation of these cells in scar formation. Furthermore, peri-lesional upregulation of endothelial CTGF expression points to a role in blood-brain barrier function and angiogenesis. In addition, CTGF appears to be a sensitive marker of early astrocyte activation.

Lesion-associated accumulation of uPAR/CD87- expressing infiltrating granulocytes, activated microglial cells/macrophages and upregulation by endothelial cells following TBI and FCI in humans

Urokinase-type plasminogen activator receptor (uPAR/CD87) together with its ligand, urokinase-type plasminogen activator (uPA), constitutes a proteolytic system associated with tissue remodelling and leucocyte infiltration. uPAR is a member of the glycosyl phosphatidyl inositol (GPI) anchored protein family. The functional role of uPAR comprises fibrinolysis by conversion of plasminogen to plasmin. In addition, uPAR promotes cell adhesion, migration, proliferation, re-organization of the actin cytoskeleton, and angiogenesis. Furthermore, uPAR is involved in prevention of scar formation and is chemoattractant to macrophages and leucocytes. In order to investigate the pathophysiological role of uPAR following human CNS injury we examined necrotic brain lesions resulting from traumatic brain injury (TBI; n = 28) and focal cerebral infarctions (FCI; n = 17) by immunohistochemistry. Numbers of uPAR+ cells and uPAR+ blood vessels were counted. Following brain damage, uPAR+ cells increased significantly within 12 h, reached a maximum after 3-4 days and remained elevated until later stages. uPAR was expressed by infiltrating granulocytes, activated microglia/macrophages and endothelial cells. Numbers of uPAR+ vessels increased in parallel subsiding earlier following FCI than post TBI. The restricted, lesion-associated accumulation of uPAR+ cells in the brain parenchyma and upregulated expression by endothelial cells suggests a crucial role for the influx of inflammatory cells and blood-brain barrier (BBB) disturbance. Through a failure in BBB function, uPAR participates in formation of brain oedema and thus contributes to secondary brain damage. In conclusion, the study defines the localization, kinetic course and cellular source of uPAR as a potential pharmacological target following human TBI and FCI.

Long-term expression of heme oxygenase-1 (HO-1, HSP-32) following focal cerebral infarctions and traumatic brain injury in humans

Extracellular heme derived from hemoglobin following hemorrhage or released from dying cells induces the expression of heme oxygenase-1 (HO-1, HSP-32) which metabolizes heme to the gaseous mediator carbon monoxide (CO), iron (Fe) and biliverdin. Biliverdin and its product bilirubin are powerful antioxidants. Thus, expression of HO-1 is considered to be a protective mechanism against oxidative stress and has been described in microglia, astrocytes and neurons following distinct experimental models of pathological alterations to the brain such as subarachnoidal hemorrhage, ischemia and traumatic brain injury (TBI) and in human neurodegenerative diseases. We have now analyzed the expression of HO-1 in human brains following TBI (n = 28; survival times: few minutes up to 6 months) and focal cerebral infarctions (FCI; n = 17; survival time: < 1 day up to months) by immunohistochemistry. Follwing TBI, accumulation of HO-1+ microglia/macrophages at the hemorrhagic lesion was detected as early as 6 h post trauma and was still pronounced after 6 months. In contrast, after FCI HO-1+ microglia/macrophages accumulated within focal hemorrhages only and were absent in non-hemorrhagic regions. Further, HO-1 was weakly expressed in astrocytes in the perifocal penumbra. In contrast to experimental data derived from rat focal ischemia, these results indicate a prolonged HO-1 expression in humans after brain injury.

"Allograft-inflammatory-factor-1 is upregulated in microglial cells in human cerebral infarctions"

Allograft inflammatory factor-1 (AIF-1) is a 17-kDa-peptide identified in rat cardiac allografts undergoing chronic rejection and in activated microglial cells in inflammatory autoimune disease of the CNS. We have investigated the expression of AIF-1 in 18 autopsy cases of human focal cerebral infarction. AIF-1-positive cells show the morphology of microglia and are CD68- but not GFAP-positive. The peptide is expressed at a low level in normal brain. In infarctions, activated microglial cells in the area of glial reaction show strongly enhanced cytoplasmic immunoreactivity. The density of AIF-1-expressing cells increases during the first three days post infarction and remains elevated until chronic cystic stages. The upregulation of AIF-1-immunoreactivity precedes the rise in expression of the S-100-protein MRP-8. We conclude that AIF-1 is a sensitive marker of human microglial activation not only in inflammation but also in non-inflammatory lesions of the CNS.

Allograft-inflammatory-factor-1 is upregulated in microglial cells in human cerebral infarctions

Allograft inflammatory factor-1 (AIF-1) is a 17-kDa-peptide identified in rat cardiac allografts undergoing chronic rejection and in activated microglial cells in inflammatory autoimune disease of the CNS. We have investigated the expression of AIF-1 in 18 autopsy cases of human focal cerebral infarction. AIF-1-positive cells show the morphology of microglia and are CD68- but not GFAP-positive. The peptide is expressed at a low level in normal brain. In infarctions, activated microglial cells in the area of glial reaction show strongly enhanced cytoplasmic immunoreactivity. The density of AIF-1-expressing cells increases during the first three days post infarction and remains elevated until chronic cystic stages. The upregulation of AIF-1-immunoreactivity precedes the rise in expression of the S-100-protein MRP-8. We conclude that AIF-1 is a sensitive marker of human microglial activation not only in inflammation but also in non-inflammatory lesions of the CNS.

Differential regulation of the monocytic calcium-binding peptides macrophage-inhibiting factor related protein-8 (MRP8/S100A8) and allograft inflammatory factor-1 (AIF-1) following human traumatic brain injury

Intracellular calcium (Ca2+) has been shown to function as second messenger and to be associated with activation of different cell types including microglia. Previously, in human focal cerebral infarctions an early expression of macrophage-related protein-8 (MRP8/ S100A8), a member of the Ca2+-binding S100-protein family, in microglia has been reported. On the other hand, a delayed activation of microglia was observed following traumatic brain injury (TBI). We therefore examined immunohistochemically microglial expression of MRP8 and allograft inflammatory factor-1 (AIF-1), identical to microglial response factor-1 (mrf-1) and ionized calcium binding adaptor molecule-1 (ibal) in human brains after TBI and in control brains. Both, MRP8 and AIF-1 are Ca2+-binding peptides which have been associated with microglial activation in experimental models and in human cerebral infarctions. Detection of AIF-1 in controls confirmed constitutive expression of this peptide in a subset of microglial cells. After TBI, the density of AIF-1+ microglia did not increase significantly. Lesional expression of AIF-1 did not significantly differ from other brain regions. Furthermore, following TBI, we found no significant differences in the density of AIF-1+ microglia as compared to controls. Microglial MRP8 expression was not detectable in controls and within the first 3 days post TBI, but increased rapidly after 3 days post TBI, suggesting a subpopulation of microglial cells to be AIF-1-/MRP8+. We conclude that the delayed expression of MRP8 and the lack of AIF-1 up-regulation in microglia after TBI is in contrast to ischemic brain lesions and might reflect different activation cascades of microglia.

Frequent expression of haemopoietic and non-haemopoietic antigens by reactive plasma cells: an immunohistochemical study using formalin-fixed, paraffin-embedded tissue

Unlike other B cells, plasma cells (PC) react with only a few antibodies against haemopoietic antigens. We investigated 36 specimens exhibiting a reactive increase in PC numbers (i.e. plasmacytosis, PC hyperplasia) with a broad panel of antibodies suitable for use on formalin-fixed, paraffin-embedded tissue, and compared the findings with those obtained in 51 cases of multiple myeloma (plasmacytoma). Regardless of the immunostaining pattern for immunoglobulin light and heavy chains, reactive PC reacted with at least two and at most six of seventeen antibodies detecting haemopoietic antigens [Ber-H2/CD30 (91%), anti-leucocyte common antigen (LCA)/CD45 (86%), KP1/CD68 (64%), MB2 (57%), 4KB5/CD45RA (37%), DF-T1/CD43 (28%), UCHL1/CD45RO (20%), L26/CD20 (17%), MT2 (14%) and Mac387 (8%)], and with at least one and at most four of six antibodies against non-haemopoietic antigens [anti-epithelial membrane antigen (EMA) (94%), anti-vimentin (77%), anti-pan-cytokeratin/KL1 (74%), BMA120 (51%) and HMB45 (14%)]. Five antibodies stained reactive PC significantly more often than neoplastic PC: Ber-H2/CD30 (p < or = 0.0000), KP1/CD68 (p < or = 0.0000), anti-LCA/CD45 (p < or = 0.0000), anti-EMA (p < or = 0.0339) and anti-pancytokeratin/KL1 (p < or = 0.0000). The more frequent and more heterogeneous expression of antigens by reactive PC suggests that the aberrant immunoreactivity of neoplastic PC in plasmacytoma is not due to the process of malignant transformation in an early step of B-cell differentiation, but could reflect the heterogeneity of antigen expression by normal PC.