Do we really need cadavers anymore to learn anatomy in undergraduate medicine?

With the availability of numerous adjuncts or alternatives to learning anatomy other than cadavers (medical imaging, models, body painting, interactive media, virtual reality) and the costs of maintaining cadaver laboratories, it was considered timely to have a mature debate about the need for cadavers in the teaching of undergraduate medicine. This may be particularly pertinent given the exponential growth in medical knowledge in other disciplines, which gives them valid justification for time in already busy medical curricula. In this symposium, the pros and cons of cadaver use in modern medical curricula were debated and audience participation encouraged.

Studies on the density, distribution, and surface phenotype of intraepithelial class II major histocompatibility complex antigen (Ia)-bearing dendritic cells (DC) in the conducting airways.

Conventional immunohistochemical analysis of airway intraepithelial class II major histocompatibility complex (Ia) expression demonstrates a morphologically heterogeneous pattern of staining, suggestive of the presence of a mixed population of endogenous antigen presenting cells. Employing a novel tissue sectioning technique in conjunction with optimal surface antigen fixation, we now demonstrate that virtually all intraepithelial Ia staining throughout the respiratory tree in the normal rat, can be accounted for by a network of cells with classical dendritic cell (DC) morphology. The density of DC varies from 600-800 per mm2 epithelial surface in the large airways, to 75 per mm2 in the epithelium of the small airways of the peripheral lung. All the airway DC costain for CD4, with low-moderate expression of a variety of other leukocyte surface markers. Both chronic (eosinophilic) inflammation and acute (neutrophilic) inflammation, caused respectively by inhalation of chemical irritants in dust or aerosolised bacterial lipopolysaccharide (LPS), are shown to be accompanied by increased intraepithelial DC density in the large airways (in the order of 50%) and up to threefold increased expression of activation markers, including the beta chain of CD11/18. The kinetics of the changes in the DC network in response to LPS mirrored those of the transient neutrophil influx, suggesting that airway intraepithelial DC constitute a dynamic population which is rapidly upregulated in response to local inflammation. These findings have important theoretical implications for research on T cell activation in the context of allergic and infectious diseases in the respiratory tract.

Downregulation of the antigen presenting cell function(s) of pulmonary dendritic cells in vivo by resident alveolar macrophages.

Class II major histocompatibility complex (Ia)-bearing dendritic cells (DC) from airway epithelium and lung parenchyma express low-moderate antigen presenting cell (APC) activity when freshly isolated. However, this function is markedly upregulated during overnight culture in a manner analogous to epidermal Langerhans cells. The in vitro "maturation" process is inhibited by coculture with pulmonary alveolar macrophages (PAM) across a semipermeable membrane, and the degree of inhibition achieved can be markedly increased by the presence of tumor necrosis factor alpha. In addition, PAM-mediated suppression of DC function is abrogated via inhibition of the nitric oxide synthetase pathway. Functional maturation of the DC is accompanied by increased expression of surface Ia, which is also inhibited in the presence of PAM. Prior elimination of PAM from DC donors via intratracheal administration of the cytotoxic drug dichloromethylene diphosphonate in liposomes, 24-72 h before lung DC preparation, achieves a comparable upregulation of APC activity, suggesting that (consistent with the in vitro data) the resident PAM population actively suppresses the APC function of lung DC in situ. In support of the feasibility of such a regulatory mechanism, electron microscopic examination of normal lung fixed by intravascular perfusion in the inflated state (which optimally preserves PAM in situ), revealed that the majority are preferentially localized in recesses at the alveolar septal junctions. In this position, the PAM are in intimate association with the alveolar epithelial surface, and are effectively separated by as little as 0.2 microns from underlying interstitial spaces which contain the peripheral lung DC population. A similar juxtaposition of airway intraepithelial DC is demonstrated with underlying submucosal tissue macrophages, where the separation between the two cell populations is effectively the width of the basal lamina.

The biceps brachii muscle and its distal insertion: observations of surgical and evolutionary relevance.

BACKGROUND: A sound understanding of the anatomy of the biceps brachii and possible anatomical variants is necessary to manage distal biceps injury. The present study was performed to define the anatomy of the biceps brachii with particular focus on the conformation of the distal biceps tendon, and its relationship of the two heads of the biceps brachii. METHODS: Twenty cadaver specimens were dissected and both qualitative and quantitative observations were made of a series of features relating to the biceps muscle and its tendon. RESULTS AND CONCLUSION: The investigation revealed anatomical variations including supernumerary heads (20%) and 'fusion' of the muscle proximal to tendon formation and a spiralling arrangement of the tendon in its approach to the radial tuberosity. The data from the present study was reviewed in the context of previous studies on the anatomy of this muscle and speculation on the evolutionary basis of the variations and their clinical implications are discussed.

Distribution and phenotype of dendritic cells and resident tissue macrophages in the dura mater, leptomeninges, and choroid plexus of the rat brain as demonstrated in wholemount preparations.

Dendritic cells (DC) are regarded as the 'sentinels' of the immune system. They play a crucial role in surveillance of peripheral tissues, trapping antigens encountered there, and migrating via the lymphatics to lymphoid organs where they interact with naive T cells thus generating antigen-specific primary immune responses. Until now it has been assumed DC are largely absent from the brain, meninges, and the choroid plexus within the ventricles. Such a situation was thought to partly explain the 'immune privileged' nature of the central nervous system (CNS). The present study of normal rat tissues using single and double immunohistochemistry reveals for the first time that extensive networks of major histocompatability (MHC) class II+/OX62+ DC are widely distributed in sites which may potentially encounter CNS antigens. These sites included the dura mater, leptomeninges, and the choroid plexus. These putative DC were negative when stained with the anti-resident tissue macrophage monoclonal antibody ED2. In addition to the rich networks of DC, dense populations of resident tissue macrophages (ED2+ and ED1+) were also demonstrated in the dura mater, leptomeninges and to a lesser extent in the choroid plexus. The presence of rich networks of DC and macrophages in the vascular and supporting tissues of the brain may play an important role in inflammatory and immune-mediated disorders affecting the CNS, including auto-immune demyelinating diseases such as multiple sclerosis.

Origin and steady-state turnover of major histocompatibility complex class II-positive dendritic cells and resident-tissue macrophages in the iris of the rat eye.

Recent studies have identified distinct but co-existing networks of resident tissue macrophages and MHC class II-positive DC present in tissues bordering the anterior chamber of the eye, a site classically regarded as 'immune-privileged'. As the DC network, present at approximately 500 cells/mm2, accounts for virtually all MHC class II immunostaining in these tissues and possesses potent capacity to stimulate primary allogenic responses in vitro, it is proposed that these cells may play an important role in immune surveillance of the anterior chamber. Tissue macrophage and DC population kinetics in the iris were examined by using X-irradiation exposure to interrupt the steady-state renewal of these cells by haematopoietically derived precursors. MHC class II-positive iris DC exhibited a half-life of approximately 3 days, a rapid turnover rate which closely resembled that of DC present in mucosal epithelia. In contrast, the resident tissue macrophage population displayed a considerably slower turnover (half-life of 10-12 days) comparable to that of epidermal Langerhans cells in the present study. Bone marrow transplantation studies confirmed the haematopoietic origin of the iris DC population. The present study provides the first estimates of the steady-state population kinetics of antigen-presenting cell populations in the iris and has important implications for understanding the role of these cells in immunological homeostasis of the anterior chamber.

Optimal methods for preparation and immunostaining of iris, ciliary body, and choroidal wholemounts.

PURPOSE: Investigations into the biology of resident and infiltrating immune cells in the uveal tract of the rodent eye have been greatly aided by the use of tissue wholemount methods. These methods offer a number of advantages over conventional histological and frozen section techniques. The purpose of this article is to provide a detailed step by step guide to aid others who may wish to use this method. METHODS: A detailed description of whole-body perfusion fixation, dissection and isolation of the iris-ciliary body from the anterior segment and the choroid from the posterior segment is provided. In addition, the techniques used to handle whole tissue pieces during single and double immunohistochemical staining protocols, as well as the staining protocols themselves, are described. RESULTS: In refining the techniques described, the author has catalogued a number of frequent problems which compromise immunohistochemical staining results. A troubleshooting guide aimed to help identify the cause of common problems and with some suggested remedies is provided. CONCLUSIONS: Although tissue wholemounts are frequently used in retinal research, a similar approach to investigating the components of the uveal tract has only recently been applied. The methods described in this article will provide sufficient detail for other investigators to obtain maximum benefit from this alternative approach and provide an additional technique to assist in their investigations of ocular immunobiology.

Endotoxin-induced uveitis. Kinetics and phenotype of the inflammatory cell infiltrate and the response of the resident tissue macrophages and dendritic cells in the iris and ciliary body.

PURPOSE: Footpad injection of bacterial lipopolysaccharide (LPS) causes pronounced anterior uveitis in susceptible species and strains. Recent studies using wholemount techniques have demonstrated the presence of rich networks of major histocompatibility complex (MHC) class II-positive dendritic cells (DC) and resident tissue macrophages in the iris and ciliary body. The aim of this investigation was to determine the immunophenotype and dynamics of the inflammatory cell infiltrate during LPS-induced anterior uveitis using the wholemount method and to examine the response of the resident tissue macrophages and DC to an acute inflammatory episode in the anterior segment. METHODS: Female Lewis rats (8 to 12 weeks old, n = 49) received a single footpad injection of 100 micrograms of LPS and were killed at various times up to 6 weeks after injection. The iris-ciliary body complex from each eye was removed intact and subdivided into segments and immunostained using a panel of monoclonal antibodies to a variety of immune cell types. RESULTS: The wholemount method clearly illustrates that during endotoxin-induced uveitis (EIU), the earliest cellular infiltrate includes small, round ED1+ mononuclear cells marginating in the iris vasculature approximately 2 hours after injection. Marginating Ox42+ polymorphonuclear leukocytes were detectable in the iris vessels approximately 4 to 6 hours after injection and were especially numerous in the ciliary body base approximately 24 hours after injection. The overall density of resident tissue macrophages (ED2+) remained largely unchanged in the course of EIU. In contrast, the total number of MHC class II-bearing (Ox6+) cells (putative dendritic cells) increased 30% in the first 6 hours and 200% by 72 hours. During the acute phase of the inflammatory response (up to 24 hours), the proportion of these cells with a dendritiform morphology decreased (93% to 50%). The number of T cells showed a biphasic response peaking at 4 to 6 hours and again at 24 hours (290 cells/mm2); however, their numbers had resumed normal low density (4 cells/mm2 to 25 cells/mm2) by 6 weeks. CONCLUSIONS: The results suggest that the neutrophilic infiltration in EIU occurs predominantly in the base of the ciliary body, whereas the monocytic and lymphocytic infiltrate occurs in the iris vasculature. Resident tissue macrophages do not undergo marked changes in density or morphology in the early course of the disease. Recruitment of T cells into the anterior segment in EIU may suggest a previously unsuspected role for these cells in the immunopathology of this disease. Changes in density and morphology of MHC class II+ DC in the iris, which persisted for at least 6 weeks, were interpreted as an increase in recruitment and migration of these cells that may serve to enhance the efficiency of immune surveillance in the anterior segment at crucial times of bacterial infection.

Resident and infiltrating immune cells in the uveal tract in the early and late stages of experimental autoimmune uveoretinitis.

PURPOSE: To investigate the dynamics of resident and infiltrating immune cells in the choroid and iris during the early and late stages of experimental autoimmune uveitis (EAU) in Lewis rats. METHODS: Uveoretinitis was induced by footpad injection of crude retinal extract and complete Freund's adjuvant with concurrent intraperitoneal injection of Bordetella pertussis. Five experimental (EAU) and five control animals (adjuvant alone) were studied at days 5, 7, 9, 11 (prodromal stage) and 42 (late stage) after immunization. Five normal animals and five animals injected with B. pertussis alone served as further controls. Immunohistochemical localization of resident macrophages, major histocompatibility complex class II (Ia)+ dendritic cells (DC), infiltrating mononuclear cells, and T cells was performed on wholemounts of isolated choroidal and iris tissue. RESULTS: Double immunolabeling confirmed the presence of distinct networks of macrophages (591 +/- 52 cells/mm2) and DC (746 +/- 38 cells/mm2) in the rat choroid. No marked qualitative and quantitative changes were observed in the density or morphologic appearance of ED2+ resident tissue macrophages in the choroid and iris before clinical onset of ocular disease. On day 11, infiltration of ED1+ monocytes had occurred in the iris but not in the choroid; however, marked infiltration of T cells was evident in both choroid (286 +/- 161 cells/mm2) and iris (196 +/- 72 cells/mm2). The total density of Ia+ cells was significantly elevated in the choroid (1152 +/- 192 cells/mm2) at day 11, and small, round Ia+ cells were two to three times more frequent than normal at both sites. The density of T cells and Ia+ cells remained significantly elevated in the choroid and iris in the late stages of EAU. CONCLUSIONS: These data suggest resident uveal tract macrophages undergo no significant alteration in density in the early stages of EAU and that the earliest site of mononuclear cellular infiltrate in EAU occurs in the iris. The increased total density of Ia+ cells in the choroid on day 11 and the presence of significantly increased numbers of small, round Ia+ cells in the iris and choroid may represent increased trafficking of DC in the eye during uveoretinitis. Furthermore, the raised numbers of Ia+ cells, concurrent with the influx of T cells, suggests Ia+ DC and macrophages may act as local antigen-presenting cells in the induction of uveoretinitis.

Evaluation of subretinal macrophage-like cells in the human fetal eye.

In many ocular diseases, macrophages are found in the subretinal space and probably play an important role in maintaining the disease process. Several issues concerning these cells are still unclear, such as their route of entry or their relation to the retinal pigment epithelium. The authors have found that the human fetal eye contains macrophage-like cells in the peripheral subretinal space. Their localization, distribution, and ultrastructural features are evaluated in 33 eyes from 17 specimens (12 to 22 weeks gestational age) by light microscopy and scanning and transmission electron microscopy. Subretinal macrophage-like cells occurred predominantly in the region of the ciliary folds. They were observed within the peripheral neural retina, beneath the retinal and ciliary pigmented epithelia, under Bruch's membrane, and in the choroid. This distribution suggests that one of the main entry pathways is through the vascular bed of the ciliary body. There were approximately nine subretinal space macrophages per 0.1 mm2 distributed in a regular fashion on the retinal pigment epithelial surface close to the ciliary folds, however, the incidence decreased further posteriorly where they were very rare. Their shapes varied from large flat cells with several long processes to more spherical cell bodies with a few membrane ruffles. There was also evidence that some of these cells had recently phagocytosed cell debris, including retinal pigment epithelial premelanosomes. Morphologically, these cells closely resemble supraependymal and epiplexus cells, the macrophage populations found on the cerebral ventricles, an environment that corresponds anatomically to the subretinal space.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural pathology of S-antigen uveoretinitis.

The morphology of S-antigen-induced uveoretinitis in guinea pigs has been studied using transmission electron microscopy. Purified bovine retinal S-antigen was shown to produce a focal chorioretinitis, characterized by selective damage to the outer retina and, almost exclusively, a mononuclear cell infiltration of the choroid and retina. Even at high doses, extensive rod outer segment damage was associated predominantly with lymphocytic and mononuclear cell infiltration. A single immunizing injection of S-antigen was sufficient to produce a chronic ocular inflammation lasting many months. Focal lesions evolved rapidly and reached an end-stage within days to weeks. Accordingly, eyes examined at any time during the disease contained areas of normal retina coexistent with fibrotic lesions. With time, the number of advanced or end stage lesions became more frequent, thereby involving a more widespread area of the retina. Examination of early stage lesions suggest that the rod outer segment is the target for immune damage in this disease, but the mechanism of damage remains to be elucidated.

Immunomorphologic studies of macrophages and MHC class II-positive dendritic cells in the iris and ciliary body of the rat, mouse, and human eye.

PURPOSE: To establish the presence of distinct populations of macrophages and MHC class II (Ia)-positive dendritic cells (DC) in the iris and ciliary body of the rat, mouse, and human eye. METHODS: Iris-ciliary body wholemounts from a variety of rat strains, balb/c mice, and human eyes were investigated by single and double immunohistochemistry, immunoelectron microscopy, and confocal microscopy to determine the phenotype, density, distribution, and location of macrophage and DC populations. RESULTS: Dendritiform and pleiomorphic macrophages were distributed in a regular array within the rat iris and ciliary body stroma (600 to 700 cells/mm2 or 7000 cells per iris). Ia+ DC were distributed in a similar regular network (400 cells/mm2 or 5500 cells per iris) within the iris stroma and ciliary epithelium. In the rat, a strain-dependent variation in the numbers of DC was noted, F344 rats displaying highest numbers of DC (962 +/- 398 cells/mm2) and WAG strain the lowest numbers (285 +/- 218 cells/mm2). Double color immunoperoxidase staining using anti-Ia and anti-pan specific macrophage monoclonal antibodies revealed that macrophages and Ia+ DC are distinct populations with only 5% to 15% overlap. Single immunoperoxidase of mouse iris and ciliary body using anti-pan macrophage and anti-Ia antibodies produced findings identical to those in rat. Preliminary studies of human tissue using confocal microscopy of immunostained whole irides also revealed a regular array of macrophages and MHC class II (HLA-DR)+ dendritiform cells. CONCLUSIONS: The mammalian iris contains rich networks of dendritiform-pleiomorphic macrophages and MHC class II+ DC. These findings suggest that the DC in the tissues lining the anterior chamber represent a rich network of putative antigen presenting cells and are the most likely candidates for transmitting antigen-specific signals from the anterior chamber in vivo and in experimental models such as ACAID: These observations have wide implications for the understanding of the pathogenesis of anterior and posterior uveitis.

Major histocompatibility complex (MHC) class II--positive dendritic cells in the rat iris. In situ development from MHC class II-negative precursors.

PURPOSE: To examine the postnatal development of major histocompatibility complex (MHC) class II-positive dendritic cells (DC) in the iris of the normal rat eye. METHODS: Single- and double-color immunomorphologic studies were performed on whole mounts prepared from rat iris taken at selected postnatal ages (2 to 3 days to 78 weeks). Immunopositive cells were enumerated, using a quantitative light microscope, and MHC class II expression on individual cells was assessed by microdensitometric analysis. RESULTS: Major histocompatibility class II-positive DCs in the iris developed in an age-dependent manner and reached adult-equivalent density and structure at approximately 10 weeks of age, considerably later than previously described in other DC populations in the rat. In contrast, the anti-rat DC monoclonal antibody OX62 revealed a population of cells present at adult-equivalent levels as early as 3 weeks after birth. Dual-color immunostaining and microdensitometric analysis demonstrated that during postnatal growth, development of the network of MHC class II-positive DCs was a consequence of the progressive increase in expression of MHC class II antigen by OX62-positive cells. CONCLUSIONS: During postnatal growth, the DC population of the iris develops initially as an OX62-positive-MHC class II-negative population, which then develops increasing MHC class II expression in situ and finally resembles classic DC populations in other tissue sites. Maturation of the iris DC population is temporally delayed compared with time to maturation in other tissue sites in the rat.

Giant vacuoles in the lining endothelium of the human Schlemm's canal after topical timolol maleate.

The outflow system was studied by light microscopy in nine human eyes that were treated with topical timolol maleate (0.5%) prior to enucleation for malignant melanoma of the choroid. The frequency of "giant vacuoles" in the lining endothelium of Schlemm's canal and the diameter of these structures was the same in a control group of eyes as in the timolol-treated series. There was no qualitative difference between the architecture of the meshwork in the control and treated groups. These morphologic findings suggested that timolol had no direct action on the outflow apparatus and did not reflect the intraocular pressure (IOP) lowering effect of the drug. The effects of anesthesia, surgical manipulations, and fixation by immersion may have masked any subtle drug effects.

Localization and characterization of major histocompatibility complex class II-positive cells in the posterior segment of the eye: implications for induction of autoimmune uveoretinitis.

PURPOSE: To identify potential antigen-presenting cells in the choroid and retina of the normal rat eye, with a view to proposing a role for such cells in the induction and perpetuation of experimental autoimmune uveoretinitis, a model of human uveoretinal inflammation. METHODS: Immunohistochemical and electron microscopic studies using a panel of monoclonal antibodies were performed on frozen sections of the perfused-fixed normal Lewis rat eye, choroid whole mounts, and cytospin preparations of cells harvested from choroid/ciliary body explant cultures. In addition, time-lapse video recordings of migratory uveal tract cells in culture were taken. RESULTS: No major histocompatibility complex class II-positive cells were found in the normal Lewis rat retina. However, at least three populations of potential antigen-presenting cells were found in the uveal tissues of the eye: classical dendritic cells expressing high levels of major histocompatibility complex class II antigen; resident dendritiform macrophages, which were negative for major histocompatibility complex class II antigen, but expressed specific macrophage markers (ED2); and blood-borne macrophages (ED1) that had emigrated from the vasculature into the tissue compartment. In addition there were small numbers of cells expressing novel markers such as markers usually found only on macrophage subsets in splenic tissue (ED3) and a recently described marker for veiled dendritic cells (OX62). Dendritic cells and resident dendritiform macrophages closely interacted with each other and with tissue cells, particularly retinal pigment epithelial cells. CONCLUSIONS: The posterior uveal tract is richly populated with classical dendritic cells expressing constitutive high levels of major histocompatibility complex class II antigen. There are also several types of macrophages with the potential to modulate immune responses in the posterior segment. Interactions among these cells and with resident tissue cells such as retinal pigment epithelial cells are probably central to the initiation of (auto)immune responses in the posterior segment of the eye.

Analysis of the cellular infiltrate in the iris during experimental autoimmune encephalomyelitis.

PURPOSE: Previous studies have shown that experimental autoimmune encephalomyelitis (EAE) and anterior uveitis (AU) develop in Lewis rats immunized with myelin basic protein (MBP). The purpose of this study was to characterize the dynamics, distribution, and phenotype of infiltrating cells in the iris during EAE-associated AU. METHODS: Lewis rats were immunized with MBP emulsified in complete Freund's adjuvant (CFA) or with CFA alone. Cellular infiltration of the iris was analyzed at various time points by immunohistochemistry of wholemounts, flow cytometry, and immunoelectron microscopy, by using monoclonal antibodies specific for monocytes/macrophages (ED1), T lymphocytes (R73, W3.25, OX8), T-cell activation markers (OX39, OX40), granulocytes (HIS48), major histocompatibility complex (MHC) class II (OX6), and neurofilament (2H3). RESULTS: MBP-immunized rats showed development of characteristic monophasic EAE, followed, after resolution of paralysis, by mild self-limited AU. Initially, focal infiltrates of round MHC class II(+) and ED1(+) cells were found in the iris. During the course of AU, the midiris became massively infiltrated with ED1(+) monocytes-macrophages, R73(+) T cells, granulocytes (HIS48(+)), and MHC class II(+) cells. The influx of T cells consisted of CD4(+) and CD8(+) cells, of which only a small fraction (<14 and 11%, respectively) expressed activation markers. The infiltrating cells accumulated in proximity to myelinated and nonmyelinated nerve bundles and in the vicinity of blood vessels in the iris. No evidence was found for demyelination or nerve degradation. Neither EAE nor AU developed in CFA-treated control rats. CONCLUSIONS: These data show that EAE-associated AU is characterized by a transient mixed cellular infiltrate consisting of monocytes-macrophages, granulocytes, and CD4 and CD8 T cells. The preferential accumulation of inflammatory cells in the vicinity of nerve fibers suggests that AU in this model may result from autoreactivity to nerve antigens.

Dendritic cells in the respiratory tract.

Studies from several laboratories on lung tissue samples from human and experimental animals have identified Ia+ cells with characteristic pleiomorphic (dendritic) morphology in the epithelium and underlying connective tissue, in both the conducting airways and in the distal lung. These dendritic cells (DC) are particularly prominent within the airway epithelium, forming a contiguous network equivalent to the Langerhans cells network of the epidermis. They may be readily concentrated from enzymatically disrupted respiratory tract tissue samples on the basis of their physical properties (notably non-adherence, lack of Fc-receptors and ultra-low density on percoll), and function as highly effective antigen presenting cells in vitro. Evidence is also accumulating that respiratory tract DC populations respond dynamically to local tissue inflammation, and as such may play a prominent role in immunoinflammatory disease processes in the airways and the distal lung.

Ultrastructural pathology of experimental autoimmune uveitis in the rat.

Experimental autoimmune uveoretinitis (EAU) has been extensively studied as a model for human posterior uveitis, however, few ultrastructural studies of EAU in the rat have been reported. In the present report we document a systematic time-course study of the posterior segment changes in the Lewis rat. The disease varied somewhat in severity in animals sacrificed at identical times after immunisation. In the prodromal stage of the disease, usually around day 14, early pathological changes included mild peripapillary vasculitis and low grade mononuclear and neutrophilic infiltration of the subretinal space with phagocytosis of the rod outer segments. The features of the severe or active diseases were most evident on day 21 and included mixed cellular infiltrate of the vitreous, subretinal serohaemorrhagic exudate, focal retinal detachment and necrosis. Outer retinal destruction was often most severe adjacent areas of retinal vasculitis. Focal monocytic subpigment epithelial microgranulomas, reminiscent of Dalen-Fuch's nodules in humans, were also identified. By day 28 and 49 active inflammation had subsided and large segments of the outer retina were completely destroyed. The retinal pigment epithelium (RPE) also showed signs of activation in the vicinity of focal retinochoroidal mononuclear infiltrates including multilayering, proliferation and increased phagocytosis. Finally, neovascularisation of the RPE by non-fenestrated capillaries derived from the retinal vasculature was evident in the late stages of the disease.

Dendritic cells and macrophages in the uveal tract of the normal mouse eye.

BACKGROUND/AIMS: Dendritic cells (DC) and macrophages are components of the immune cell populations in the uveal tract whose density, distribution, turnover, and function may play a role in the maintenance of immunological homeostasis in the eye. Little is known of these cells in the mouse eye despite this being the predominant experimental model in many studies of ocular immune responses and immunoinflammatory mediated eye diseases. The aim of the present study was to obtain further immunophenotypic data on resident tissue macrophages and DC populations in the mouse uveal tract. METHODS: Pieces of iris, ciliary body, and choroid dissected from perfusion fixed BALB/c mice were incubated whole in a variety of anti-macrophage and DC monoclonal antibodies (mAbs). Labelled cells were visualised using either single or double immunoperoxidase techniques. RESULTS: Quantitative analysis and double immunolabelling revealed that 80% of F4/80(+) cells (a mAb that recognises both DC and macrophages) in the iris are macrophages (SER4(+)). The iris contained a network of Ia+ cells (412 (SD 130) cells/mm2) of which two thirds appear to be DC. A similar pattern was observed in the ciliary body and choroid. Only a few DC in the uveal tract were very weakly reactive for mAbs which recognise B7-1 (CD80), B7-2 (CD86), beta2 integrin (mAb N418), and multivesicular bodies associated with antigen presentation (mAb M342). CONCLUSIONS: The present study reveals that the mouse uveal tract, like the rat, contains rich networks of DC and resident tissue macrophages. The networks of resident tissue macrophages in the mouse uveal tract closely resemble similar networks in non-ocular tissues. The phenotype of uveal tract DC suggests they are in the "immature" phase of their life cycle, similar to Langerhans cells of the skin, thus implying their role in situ within the eye is antigen capture and not antigen presentation.

Human fetal iridocorneal angle: a light and scanning electron microscopic study.

The iridocorneal angle and inner layers of the trabecular meshwork in human fetal eyes were studied by scanning electron microscopy. Tissue from 32 eyes of 17 fetuses with a gestational age from 12 to 22 weeks were investigated in order to determine the morphological changes in the cellular lining of the anterior chamber angle recess during development. The findings indicate that, although hexagonal corneal endothelial profiles extend almost to the angle apex in a few of the younger eyes examined (12-14 weeks), the lining is always perforated by a few discrete intercellular gaps (2-6 microns diameter). As development progresses it becomes clearer that the maturing meshwork is lined by uveal trabecular endothelial cells which are morphologically distinguishable from corneal endothelium. The frequency and size of the gaps between the inner uveal trabecular endothelial cells increase and are well developed by 18-20 weeks, clearly providing a route of communication between the fetal anterior chamber and the developing intercellular spaces in the primitive trabecular tissue. The implications of these observations on the 'Barkan's membrane' theory of congenital glaucoma are discussed.