Accumulation, distribution and phenotype heterogeneity of mast cells (MC) in human brains with neurocysticercosis.

Neurocysticercosis (NCC) is one of the most common parasitic brain infections in the world NCC can cause widely varied clinical manifestations, mainly due to the host immune-inflammatory response. The immunological hallmark of the infection with helminth parasites is infiltration into the inflamed mucosa of the gastrointestinal tract of numerous mast cells. It has been postulated that mediators released by activated mast cells might contribute to the local inflammatory response. Since data concerning the association of mast cells with neurocysticercosis are not available, the aim of our study is to determine the distribution and phenotypes of mast cells in human brain infested by cysticerci. The study was performed on 20 human autopsy brains. Mast cells (MC) were identified by means of immunohistochemical method using specific MC tryptase and chymase monoclonal antibodies. In the control brains, mast cells were very few and showed a very sparse distribution. They had been occasionally found in meninges and in perivascular areas of some brain blood vessels. Those cells were mainly tryptase-chymase phenotype (MCTTC). In contrast, in the brain sections with neurocysticercosis, mast cells were numerous. A striking feature of identified mast cells was their phenotype heterogeneity. The tryptase mast cells (MCT) phenotype dominated over the tryptase-chymase (MCTC) phenotype. MCT infiltrated mainly meninges and brain parenchyma around cysts with viable and necrotic parasites. MCTC infiltrated perivascular area of the blood vessels penetrating to the depth of the brain. Summarising, this is the first report which documents the accumulation and phenotype heterogeneity of mast cells in human brains with neurocysticercosis. Our findings suggest that the effector mechanism responsible for the host responses to the parasitic infection that involves numerous mast cells in the human brain may be very important for pathomechanism of this disease.

Phenotype of mast cells in the brain tumor. Capillary hemangioblastoma.

Mast cells (MC) are heterogenous cell population. In normal human brain they are not numerous. Increases in number of mast cells within CNS occur in certain disease states including neoplasms. In capillary hemangioblastoma several authors reported mast cells as a fourth cell type of the tumor. The aim of the present study was to examine phenotype and distribution of MC in cerebellar capillary hemangioblastoma by means of specific immunological markers. Study was performed on the tumor of ten affected individuals. Tumor specimens of seven cases were fixed in formalin and embedded in paraffin wax. Additional three tumours were fresh-frozen samples. Mast cells were identified with two monoclonal antibodies generated against tryptase and chymase. In all capillary hemangioblastomas mast cells were numerous exclusively in the tumor mass and only occasionally found in adjacent or far from the tumor located areas of the cerebellum. The cells contained tryptase and chymase. At periphery of hemangioblastomas some mast cells underwent degeneration and calcification. Our results confirm previous observations that mast cells are numerous in the capillary hemangioblastoma and show that most of these cells are tryptase/chymase phenotype (MCTC).

Expression of cyclooxygenase-2 in astrocytes of human brain after global ischemia.

COX-2 expression, an inducible form of cyclooxygenase was studied in human brain after ischemia-reperfusion. Previously, a prominent COX-2 upregulation was described in neurons few hours or days after ischemia but little is known about COX-2 expression in non-neuronal cells participating in post-ischemic inflammation. Aim of the study was to examine COX-2 expression in activated glial cells of individuals, who died two or more weeks after resuscitation. In the cerebral cortex of these individuals ischemic necrosis was more or less widespread. In some brain areas numerous microglial cells were found. At the centre of the necrosis high expression of COX-2 was detected in macrophages, polymorphic cells and leukocytes. At the margin of necrosis hypertrophic astrocytes were COX-2 immunopositive. Expression of COX-2 was observed also in the wall of blood vessels of necrotic brain areas and in meninges. The results of the study suggest that in the late period after global ischemia reactive and hypertrophic astrocytes and macrophages may be the major sources of prostaglandins in the human brain.

Constitutive expression of cyclooxygenase-2 (COX-2) in developing brain. A. Choroid plexus in human fetuses.

It is believed that prostanoids produced by COX-1 activity are essential for the physiological functions of tissues while those produced by COX-2 lead to various pathological changes in these tissues. Brain is an exceptional organ where in some neurons COX-2 mRNA and its protein are constitutively expressed. Since some prostaglandins may play an important role in the control of blood-brain barrier and cerebral blood flow the purpose of the present study was to examine the COX-2 expression in choroid plexus, which participate in the nutrition of brain parenchyma of human fetuses. Study was performed on 25 brains of human fetuses from 12 to 38 weeks of gestation. In light and electron microscopy characteristic developmental transformation of choroid morphology was observed. In young fetuses from 12 to 20 week of gestation epithelial cells of choroid plexus are cuboidal, contain large amount of glycogen storage and their nuclei are COX-2 immunopositive. From 25 week of gestation until term the amount of glycogen in the choroid plexus diminishes, some apical nuclei are shifted toward central parts of the cells and number of cytoplasm organelles increases. In these cells expression of COX-2 protein is located in cytoplasm but epithelial nuclei are immunonegative. Our results provided evidence that COX-2 is constitutively expressed in the developing human choroid plexus. Different localization of COX-2 in choroid epithelial cells suggests that this enzyme may play a different role in various periods of the choroid plexus development.

Morphological forms and localization of microglial cells in the developing human cerebellum.

There are relatively few studies on microglia of human developing brain thus function and location of these cells at this period of life are unknown. Moreover, all of them concentrated on the cells in very early period of fetal life. To achieve further insight into the participation of microglial cells in the development of the central nervous system the brains of fetuses, newborns and infants were examined by means of immunological markers: Ricinus communis agglutinin-1 (RCA-1) and ferritin antiserum. Brains of 12 fetuses and infants ranging in age from 14 weeks of gestation to 5 months after birth were used in the study. The fetuses were derived following spontaneous abortions. In pre-term and term newborns the cause of death was of maternal origin (placental insufficiency) or accidental sudden death. Coronal blocks of cerebellum cut into 5 microns thick sections were used in the study. The developing microglial cells were detected by both markers (RCA-1 and anti-ferritin). Ricinus communis agglutinin recognizes carbohydrate residues on the surfaces of microglial and endothelial cells. Therefore, in the sections incubated with this lectin brain vessels as well as microglia were visualized. The second microglial marker anti-ferritin serum detected precisely all morphological subpopulations of microglia including ameboid and ramified cells but endothelial cells remained immunonegative. Therefore, in 14 weeks of gestation only round ameboid microglia were ferritin-immunopositive in cerebellum. These cells were localized at the periphery of the periventricular, germinal matrix and were surrounding a group of nerve cells of the developing dentate nucleus. In 16 week-old fetuses ameboid cells were present in the hilus and between gyri of the dentate nucleus. The ferritin-positive microglial cells on the convolutions of the dentate nucleus gyri manifested as the cells with short fine branched processes and scanty cytoplasm. In cerebellum of the 20 week-old fetuses the subpopulation of branched (ramified) microglia were more numerous than ameboid cells. Ameboid cells were present mainly in the intermediate zone of the future white matter and ramified cells penetrated the inner (at the one third of its thickness) part of the developing internal granular layer of cerebellar cortex. The upper part of cerebellar cortex was colonized by microglia between 24-28 weeks of gestation. In cerebellum of fetuses over 28 weeks of gestation numerous microglial cells infiltrated mainly the Purkinje cell layer, first in the vermis, later in the hemispheres. From 36 weeks of gestation to the birth ferritin-immunopositive microglial cells gradually disappeared from the cerebellar cortex. The microglia of the term newborns and of a 5 month-old child manifested mainly as ramified cells located in the white matter. The results of our study lead to the conclusion that the localization of microglial cells in the brain structure and their morphological forms correlate precisely with the appropriate stages of the brain development.