Trabecular Meshwork And Outflow Pathways

There is an extensive literature on the phagocytic properties of trabecular cells (see review, Ref. 71). In addition, the concept of a population of wandering phagocytes or RTMs within the trabecular meshwork (Fig. 7) is well accepted and pre-dates the availability of monoclonal antibodies and immunophenotypic analysis. Traditional ultrastructural studies have suggested these cells, which have all the classical morphological characteristics of mononuclear phagocytes, play a role in aiding...

Introduction

Most autoimmune diseases are human leukocyte antigen (HLA)-associated. The reason for this is most likely the individualization of the immune response by HLA-mediated antigen presentation to T cells. The following provides a basic introduction to this phenomenon. With few exceptions, all nucleated human cells express HLA class I molecules on their surfaces. These consist of a heavy chain encoded by one of the three HLA class I loci, HLA-A, HLA-B, or HLA-C on chromosome 6, and a...

IgE Receptors

IgE is known as the main antibody involved in allergic inflammatory processes such as asthma, atopic dermatitis, and allergic rhinitis. Two distinct receptors have been demonstrated for IgE the high-affinity IgE receptor (FceRI), and the low-affinity IgE receptor (FceRII). In humans, the high-affinity receptor has two forms the classical tetrameric FceRI (aj3y2), which is constitutively expressed on effector cells of anaphylaxis (mast cells, basophils), and the trimeric form (ay2), which is...

The Dendritic Cell As An Antigenpresenting Cell

In general, the subset of antigen-presenting cells (APCs) that is uniquely well equipped for presenting antigen to T cells and is regarded as sentinels for inducing immune responses is the dendritic cell (DC) subpopulation (1,2). T cells recognize antigens presented by major histocompatibility complex (MHC) molecules expressed on the APCs, and the subsequent interactions determine the differentiation pathway for the T cell. APCs are made up of a heterogeneous family of cells that is able to...

Eyeassociated Lymphoid Tissue As An Entrance Site For Immunological Events

Some organs of the human body (anterior eye chamber, brain, placenta, testicle) are characterized by a special immunological state of reduced activation of the specific and nonspecific immune systems. This condition of local immune suppression, termed the immune privilege, is expressed in delayed or totally suppressed rejection of allogenic transplantations in these organs (17,18) this is illustrated by maintenance of the immunophenotypically immature placenta in the maternal organism as well...

Antigen Presenting Cells and Molecular Mechanisms Underlying Induction of Immune Deviation

Wayne Streilein,t and A. Paiman Ghafoori Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, U.S.A. Immune privilege in the eye is known to protect the precious microanatomy of the visual axis from the inflammatory assault of an immune response, thereby avoiding any damage to accurate vision, while permitting expression of protective adaptive immunity. A fine balance between the protective and detrimental effects...

Central Cornea

It has been accepted for some time that the central cornea was devoid of MHC class II+ cells (or Ia+ in rodents) (12-15) however, they were recognized as being present in the peripheral epithelium and stroma of the murine cornea (14,15). Identification of ATPase+ dendriform cells in the peripheral and pericentral murine cornea (13,14,16) appeared to confirm the presence of DCs in these zones. This concept of a centripetal gradient in density corneal epithelial LCs was found to be true of a...

APCs Also Traffic To The Effector Sites

Immature dendritic cells also enter the effector sites of the mucosal immune system (104). Large numbers are present in the lamina propria of the intestines (105) and respiratory system (106), and significant numbers also are present in liver (107,108), salivary glands (109,110), lacrimal glands (13,111), and conjunctiva (111,112). In the present context, it may be appropriate to note that they also are present in the cornea (113,114). The immature dendritic cells' constitutive phagocytic...

Macrophages in the Iris Ciliary Body and Choroid

Conventional histological and ultrastructural studies revealed macrophages in the human iris stroma to early microscopists. In particular, their propensity to phagocytose melanin shed from iris pigment epithelium throughout life make them a characteristic feature of histological preparations of human eyes where some were thought to represent a subpopulation of Clump cells (61). More recently, studies of normal rat and mouse iris, ciliary body, and choroid revealed rich networks ( 600-800 cells...

Other Macrophage Populations In The Eye Vitreous Macrophages or Hyalocytes

A little studied population of CD11b+ CD68+ CD163+ RTMs is situated between the inner retinal surface and the vitreous membrane (Fig. 9). These cells, sometimes referred to as hyalocytes (109), are considered scavengers of this tissue interface and probably arise from the population of macrophages that phagocytose the hyaloid vessels and tunica vasculosa lentis during development (102). It is worth noting that they may act as a source of contamination in 'retinal preparations' (especially in...

DC in the Uveal Tract of the

Many early studies, performed on conventionally sectioned ocular tissue, either failed to reveal any MHC class II+ cells or revealed only occasional, scattered cells in the normal uveal tract (see review, Ref. 71). In the early and mid-1990s a number of groups, including our own, discovered a contiguous network of MHC class II+ DCs in the iris, ciliary, and choroid of mouse, rat, and human eyes (58,60, 62-65,72). DCs in the uveal tract (Figs. 4B, 5B, and 6B) display a variety of forms from...

APCs In Initiation Of Mucosal Immune Responses

Antigens can be taken up across the epithelial linings of various mucosal tissues, and many of these tissues then generate robust sIgA responses. Most of our knowledge about this response has been gained from studies of gut-associated lymphoid tissue in rodents and of human tonsils. The major inductive sites of the mucosal immune system are follicles and organized aggregates of follicles, exemplified by Peyer's patches in the intestine and referred to generically as mucosa-associated lymphoid...

Ctype Lectins Dec205 And Mmr As Prototype Receptors With Different Pathways

Recently, many different C-type lectins have been characterized in DCs, ranging from molecules containing single carbohydrate recognition domains CRDs , to deca-lectins that comprise 10 CRDs 21 . The presence of CRDs implies that glycoproteins are the most likely candidate. The expression of different CRDs within one receptor allows the defined binding of specific sugars. For example, the mannose receptor, MMR CD206 22 , but not DC-SIGN CD209 23 or Blood-DC-Antigen-2 BDCA-2 24 , binds to...

Similarities And Differences Of Dendritic Cells To Monocytes And Macrophages

To distinguish self from non-self, antigen DCs and Mphs are equipped with various pathogen recognition receptors to respond to microbial infections, such as Toll-like receptors, scavenger receptors, or indirectly though receptors binding complement- or antibody-trapped antigens. Both cell types also reside in almost all peripheral tissues as sentinels of the immune system 1,2 . Besides these similarities, there are some striking functional differences qualifying DCs as separate cell types and...

Lacrimal Secretory Epithelial Functional Design Features That Expose Autoantigens

Dimeric IgA dIgA is produced by plasma cells that reside in the subepithelial tissue space of the lacrimal glands. According to a current cellular model, summarized in Figure 1, the internal membrane traffic pathway lacrimal epithelial cells use to transfer IgA to the nascent lacrimal gland fluid intersects with the pathways they use to secrete the proteins they have synthesized themselves and also with the pathways they use to deliver proteins to the lysosomes. dIgA is Y plgR secretory protein...

Limbus

Within the limbus and conjunctiva, putative DCs are abundant both in the epithelium classical LC-like cells and in the subepithelial connective tissue Fig. 2A-C of a number of species 13,16,40,41 . The subepithelial populations co-exist alongside typical RTM which display a perivascular distribution 42 . Figure 2 Confocal images of rat corneal-limbal wholemount stained with anti-MHC class II mAb as shown in A illustrates the entire confocal Z-series optical sections , which includes the...

IgE Receptor Crosslinking And Activation Of Apcs

The first direct evidence of DC and IgE interaction was via immunohistochemical and immunoelectron microscope demonstrations of IgE bearing LCs in AD patients 29 . Subsequently, FceRI expression in normal human LCs was also demonstrated simultaneously by two groups 30,31 . Binding of an allergen to the FceRI on APCs from an atopic individual who expresses high levels of this receptor leads to receptor cross-linking and subsequent activation of these cells. In nonatopic individuals this is not...