1
|
Immune responses to injury and their links to eye disease. Transl Res 2021; 236:52-71. [PMID: 34051364 PMCID: PMC8380715 DOI: 10.1016/j.trsl.2021.05.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/12/2021] [Accepted: 05/24/2021] [Indexed: 12/31/2022]
Abstract
The eye is regarded as an immune privileged site. Since the presence of a vasculature would impair vision, the vasculature of the eye is located outside of the central light path. As a result, many regions of the eye evolved mechanisms to deliver immune cells to sites of dysgenesis, injury, or in response to the many age-related pathologies. While the purpose of these immune responses is reparative or protective, cytokines released by immune cells compromise visual acuity by inducing inflammation and fibrosis. The response to traumatic or pathological injury is distinct in different regions of the eye. Age-related diseases impact both the anterior and posterior segment and lead to reduced quality of life and blindness. Here we focus attention on the role that inflammation and fibrosis play in the progression of age-related pathologies of the cornea and the lens as well as in glaucoma, the formation of epiretinal membranes, and in proliferative vitreoretinopathy.
Collapse
Key Words
- 2ryERM
- A T-helper cell that expresses high levels of IL-17 which can suppress T-regulatory cell function
- A cytokine expressed early during inflammation that attracts neutrophils
- A cytokine expressed early during inflammation that attracts neutrophils, sometimes referred to as monocyte chemoattractant protein-1 (MCP-1))
- A mouse model that lacks functional T and B cells and used to study the immune response
- A pigmented mouse strain used for research and known to mount a primarily Th1 response to infection
- A protein encoded by the ADGRE1 gene that, in mice, is expressed primarily on macrophages
- A strain of pigmented mice used in glaucoma research
- ACAID
- APCs
- ASC
- An albino mouse strain used for research and known to mount a primarily Th2 response to infection
- Antigen Presenting Cells, this class includes dendritic cells and monocytes
- BALB/c
- BM
- C57BL6
- CCL2
- CD45
- CNS
- CXCL1
- Central Nervous System
- Cluster of differentiation 45 antigen
- DAMPs
- DBA/2J
- EBM
- ECM
- EMT
- ERM
- Epithelial Basement Membrane
- F4/80
- FGF2
- HA =hyaluronic acid
- HSK
- HSP
- HSPGs
- HSV
- ICN
- IL-20
- IL6
- ILM
- IOP
- Inner (or internal) limiting membrane
- Interleukin 6
- Interleukin-20
- MAGP1
- MHC-II
- Major histocompatibility complex type II, a class of MHC proteins typically found only on APCs
- Microfibril-associated glycoprotein 1
- N-cad
- N-cadherin
- NEI
- NK
- National Eye Institute
- Natural killer T cells
- PCO
- PDGF
- PDR
- PVD
- PVR
- Platelet derived growth factor
- Posterior capsular opacification
- RGC
- RPE
- RRD
- Rag1-/-
- Retinal ganglion cells
- Retinal pigment epithelial cells
- SMAD
- Sons of Mothers Against Decapentaplegic, SMADs are a class of molecules that mediate TGF and bone morphogenetic protein signaling
- T-helper cell 1 response, proinflammatory adaptive response involving interferon gamma and associated with autoimmunity
- T-helper cell 2 response involving IgE and interleukins 4,5, and 13, also induces the anti-inflammatory interleukin 10 family cytokines
- T-regulatory cell
- TG
- TGF1
- TM
- TNF
- Th1
- Th17
- Th2
- Transforming growth factor 1
- Treg
- Tumor necrosis factor a cytokine produced during inflammation
- VEGF
- Vascular endothelial growth factor
- WHO
- World Health Organization
- anterior chamber immune deviation
- anterior subcapsular cataracts
- basement membrane
- damage-associated molecular patterns
- epiretinal membrane
- epiretinal membrane secondary to disease pathology
- epithelial-mesenchymal transition
- extracellular matrix
- fibroblast growth factor 2, also referred to as basic FGF
- heat shock protein
- heparan sulfate proteoglycans
- herpes simplex virus
- herpes stromal keratitis
- iERM
- idiopathic epiretinal membrane
- intraepithelial corneal nerves
- intraocular pressure
- mTOR
- mechanistic target of rapamycin, a protein kinase encoded by the MTOR genes that regulates a variety of signal transduction events including cell growth, autophagy and actin cytoskeleton
- posterior vitreous detachment
- proliferative diabetic retinopathy
- proliferative vitreoretinopathy
- rhegmatogenous (rupture, tear) retinal detachment
- trabecular meshwork
- trigeminal ganglion
- αSMA
- α−Smooth muscle actin, a class of actin expressed in mesenchymal cells
Collapse
|
2
|
Menko AS, DeDreu J, Logan CM, Paulson H, Levin AV, Walker JL. Resident immune cells of the avascular lens: Mediators of the injury and fibrotic response of the lens. FASEB J 2021; 35:e21341. [PMID: 33710665 PMCID: PMC8200928 DOI: 10.1096/fj.202002200r] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 12/09/2020] [Accepted: 12/21/2020] [Indexed: 12/12/2022]
Abstract
Tissues typically harbor subpopulations of resident immune cells that function as rapid responders to injury and whose activation leads to induction of an adaptive immune response, playing important roles in repair and protection. Since the lens is an avascular tissue, it was presumed that it was absent of resident immune cells. Our studies now show that resident immune cells are a shared feature of the human, mouse, and chicken lens epithelium. These resident immune cells function as immediate responders to injury and rapidly populate the wound edge following mock cataract surgery to function as leader cells. Many of these resident immune cells also express MHCII providing them with antigen presenting ability to engage an adaptive immune response. We provide evidence that during development immune cells migrate on the ciliary zonules and localize among the equatorial epithelial cells of the lens adjacent to where the ciliary zonules associate with the lens capsule. These findings suggest that the vasculature‐rich ciliary body is a source of lens resident immune cells. We identified a major role for these cells as rapid responders to wounding, quickly populating each wound were they can function as leaders of lens tissue repair. Our findings also show that lens resident immune cells are progenitors of myofibroblasts, which characteristically appear in response to lens cataract surgery injury, and therefore, are likely agents of lens pathologies to impair vision like fibrosis.
Collapse
Affiliation(s)
- A Sue Menko
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Department of Ophthalmology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - JodiRae DeDreu
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Caitlin M Logan
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Heather Paulson
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Alex V Levin
- Department of Ophthalmology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Wills Eye Hospital, Philadelphia, PA, USA
| | - Janice L Walker
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Department of Ophthalmology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| |
Collapse
|
3
|
Walker JL, Menko AS. Immune cells in lens injury repair and fibrosis. Exp Eye Res 2021; 209:108664. [PMID: 34126081 DOI: 10.1016/j.exer.2021.108664] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/26/2021] [Accepted: 05/28/2021] [Indexed: 12/18/2022]
Abstract
Immune cells, both tissue resident immune cells and those immune cells recruited in response to wounding or degenerative conditions, are essential to both the maintenance and restoration of homeostasis in most tissues. These cells are typically provided to tissues by their closely associated vasculatures. However, the lens, like many of the tissues in the eye, are considered immune privileged sites because they have no associated vasculature. Such absence of immune cells was thought to protect the lens from inflammatory responses that would bring with them the danger of causing vision impairing opacities. However, it has now been shown, as occurs in other immune privileged sites in the eye, that novel pathways exist by which immune cells come to associate with the lens to protect it, maintain its homeostasis, and function in its regenerative repair. Here we review the discoveries that have revealed there are both innate and adaptive immune system responses to lens, and that, like most other tissues, the lens harbors a population of resident immune cells, which are the sentinels of danger or injury to a tissue. While resident and recruited immune cells are essential elements of lens homeostasis and repair, they also become the agents of disease, particularly as progenitors of pro-fibrogenic myofibroblasts. There still remains much to learn about the function of lens-associated immune cells in protection, repair and disease, the knowledge of which will provide new tools for maintaining the core functions of the lens in the visual system.
Collapse
Affiliation(s)
- Janice L Walker
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA; Department of Ophthalmology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - A Sue Menko
- Department of Pathology, Anatomy and Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA; Department of Ophthalmology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA.
| |
Collapse
|
4
|
Álvarez-Hernán G, de Mera-Rodríguez JA, Hernández-Núñez I, Marzal A, Gañán Y, Martín-Partido G, Rodríguez-León J, Francisco-Morcillo J. Analysis of Programmed Cell Death and Senescence Markers in the Developing Retina of an Altricial Bird Species. Cells 2021; 10:cells10030504. [PMID: 33652964 PMCID: PMC7996935 DOI: 10.3390/cells10030504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/19/2021] [Accepted: 02/23/2021] [Indexed: 12/30/2022] Open
Abstract
This study shows the distribution patterns of apoptotic cells and biomarkers of cellular senescence during the ontogeny of the retina in the zebra finch (T. guttata). Neurogenesis in this altricial bird species is intense in the retina at perinatal and post-hatching stages, as opposed to precocial bird species in which retinogenesis occurs entirely during the embryonic period. Various phases of programmed cell death (PCD) were distinguishable in the T. guttata visual system. These included areas of PCD in the central region of the neuroretina at the stages of optic cup morphogenesis, and in the sub-optic necrotic centers (St15–St20). A small focus of early neural PCD was detected in the neuroblastic layer, dorsal to the optic nerve head, coinciding with the appearance of the first differentiated neuroblasts (St24–St25). There were sparse pyknotic bodies in the non-laminated retina between St26 and St37. An intense wave of neurotrophic PCD was detected in the laminated retina between St42 and P8, the last post-hatching stage included in the present study. PCD was absent from the photoreceptor layer. Phagocytic activity was also detected in Müller cells during the wave of neurotrophic PCD. With regard to the chronotopographical staining patterns of senescence biomarkers, there was strong parallelism between the SA-β-GAL signal and p21 immunoreactivity in both the undifferentiated and the laminated retina, coinciding in the cell body of differentiated neurons. In contrast, no correlation was found between SA-β-GAL activity and the distribution of TUNEL-positive cells in the developing tissue.
Collapse
Affiliation(s)
- Guadalupe Álvarez-Hernán
- Área de Biología Celular Departamento de Anatomía Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; (G.Á.-H.); (J.A.d.M.-R.); (I.H.-N.); (G.M.-P.)
| | - José Antonio de Mera-Rodríguez
- Área de Biología Celular Departamento de Anatomía Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; (G.Á.-H.); (J.A.d.M.-R.); (I.H.-N.); (G.M.-P.)
| | - Ismael Hernández-Núñez
- Área de Biología Celular Departamento de Anatomía Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; (G.Á.-H.); (J.A.d.M.-R.); (I.H.-N.); (G.M.-P.)
| | - Alfonso Marzal
- Área de Zoología, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain;
| | - Yolanda Gañán
- Área de Anatomía y Embriología Humana, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain;
| | - Gervasio Martín-Partido
- Área de Biología Celular Departamento de Anatomía Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; (G.Á.-H.); (J.A.d.M.-R.); (I.H.-N.); (G.M.-P.)
| | - Joaquín Rodríguez-León
- Área de Anatomía y Embriología Humana, Departamento de Anatomía, Biología Celular y Zoología, Facultad de Medicina, Universidad de Extremadura, 06006 Badajoz, Spain;
- Correspondence: (J.R.-L.); (J.F.-M.)
| | - Javier Francisco-Morcillo
- Área de Biología Celular Departamento de Anatomía Biología Celular y Zoología, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain; (G.Á.-H.); (J.A.d.M.-R.); (I.H.-N.); (G.M.-P.)
- Correspondence: (J.R.-L.); (J.F.-M.)
| |
Collapse
|
5
|
Francisco-Morcillo J, Bejarano-Escobar R, Rodríguez-León J, Navascués J, Martín-Partido G. Ontogenetic cell death and phagocytosis in the visual system of vertebrates. Dev Dyn 2014; 243:1203-25. [PMID: 25130286 DOI: 10.1002/dvdy.24174] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 07/04/2014] [Accepted: 07/25/2014] [Indexed: 12/25/2022] Open
Abstract
Programmed cell death (PCD), together with cell proliferation, cell migration, and cell differentiation, is an essential process during development of the vertebrate nervous system. The visual system has been an excellent model on which to investigate the mechanisms involved in ontogenetic cell death. Several phases of PCD have been reported to occur during visual system ontogeny. During these phases, comparative analyses demonstrate that dying cells show similar but not identical spatiotemporally restricted patterns in different vertebrates. Additionally, the chronotopographical coincidence of PCD with the entry of specialized phagocytes in some regions of the developing vertebrate visual system suggests that factors released from degenerating cells are involved in the cell migration of macrophages and microglial cells. Contradicting this hypothesis however, in many cases the cell corpses generated during degeneration are rapidly phagocytosed by neighboring cells, such as neuroepithelial cells or Müller cells. In this review, we describe the occurrence and the sites of PCD during the morphogenesis and differentiation of the retina and optic pathways of different vertebrates, and discuss the possible relationship between PCD and phagocytes during ontogeny.
Collapse
|
6
|
Bejarano-Escobar R, Blasco M, Durán AC, Martín-Partido G, Francisco-Morcillo J. Chronotopographical distribution patterns of cell death and of lectin-positive macrophages/microglial cells during the visual system ontogeny of the small-spotted catshark Scyliorhinus canicula. J Anat 2013; 223:171-84. [PMID: 23758763 DOI: 10.1111/joa.12071] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/16/2013] [Indexed: 01/15/2023] Open
Abstract
The patterns of distribution of TUNEL-positive bodies and of lectin-positive phagocytes were investigated in the developing visual system of the small-spotted catshark Scyliorhinus canicula, from the optic vesicle stage to adulthood. During early stages of development, TUNEL-staining was mainly found in the protruding dorsal part of the optic cup and in the presumptive optic chiasm. Furthermore, TUNEL-positive bodies were also detected during detachment of the embryonic lens. Coinciding with the developmental period during which ganglion cells began to differentiate, an area of programmed cell death occurred in the distal optic stalk and in the retinal pigment epithelium that surrounds the optic nerve head. The topographical distribution of TUNEL-positive bodies in the differentiating retina recapitulated the sequence of maturation of the various layers and cell types following a vitreal-to-scleral gradient. Lectin-positive cells apparently entered the retina by the optic nerve head when the retinal layering was almost complete. As development proceeded, these labelled cells migrated parallel to the axon fascicles of the optic fiber layer and then reached more external layers by radial migration. In the mature retina, lectin-positive cells were confined to the optic fiber layer, ganglion cell layer and inner plexiform layer. No evident correlation was found between the chronotopographical pattern of distribution of TUNEL-positive bodies and the pattern of distribution of lectin-labelled macrophages/microglial cells during the shark's visual system ontogeny.
Collapse
Affiliation(s)
- Ruth Bejarano-Escobar
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | | | | | | | | |
Collapse
|
7
|
Rodríguez-Gallardo L, Lineros-Domínguez MDC, Francisco-Morcillo J, Martín-Partido G. Macrophages during retina and optic nerve development in the mouse embryo: relationship to cell death and optic fibres. ACTA ACUST UNITED AC 2005; 210:303-16. [PMID: 16217650 DOI: 10.1007/s00429-005-0051-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2005] [Indexed: 10/25/2022]
Abstract
We compared the spatial and temporal patterns of distribution of macrophages, with patterns of naturally occurring cell death and optic fibre growth during early retina and optic nerve development, in the mouse. We used embryos between day 10 of embryogenesis (E10; before the first optic fibres are generated in the retina) and E13 (when the first optic fibres have crossed the chiasmatic anlage). The macrophages and optic axons were identified by immunocytochemistry, and the apoptotic cells were detected by the TUNEL technique, which specifically labels fragmented DNA. Cell death was observed in the retina and the optic stalk long before the first optic axons appeared in either region. Subsequently, specialized F4/80-positive phagocytes were detected in chronological and topographical coincidence with cell death, which disappeared progressively. As development proceeded, the pioneer ganglion cell axons reached the regions where the macrophages were located. As the number of optic fibres increased, the macrophages disappeared. Therefore, cell death, accompanied by macrophages, preceded the growth of fibres in the retina and the optic nerve. Moreover, these macrophages synthesized NGF and the optic axons were p75 neurotrophin receptor (p75(NTR))- and TrkA-positive. These findings suggest that macrophages may be involved in optic axon guidance and fasciculation.
Collapse
Affiliation(s)
- Lucía Rodríguez-Gallardo
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Extremadura, Avda de Elvas s/n, 06071, Badajoz, Spain.
| | | | | | | |
Collapse
|
8
|
Abstract
The aim of the present work has been to demonstrate the inducing capacity of living homogenous undamaged tissues from adult frogs. Tissues from the eyes of adult frogs Xenopus laevis: retina (R), pigmented epithelium (PE), lens epithelium (LE), and the forebrain (B) as a control, were tested for their inducing capacity using early gastrula ectoderm. To exclude the possibility of ad-mixture of inducing cells in early gastrula ectoderm the transfilter induction technique was used throughout. The results show that the tissues used in the cases of most intense induction tended to induce similar cell types: both R and PE induce R + PE together with adjoining neural cells and secondary lens cells. LE induces lentoids (L) and B cells induce neuroids. In each case epidermis surrounds the explants filled with ectomesenchyme (EM) and melanophores (M). Immunofluorescence reactions clarified the nature of lens cells. This discovery indicates that cells of adult tissues continue throughout life producing substances which are able to promote the appearance of cells of the same type during development. Probably they also serve to mediate interrelations between cells of these tissues, regulating the stability of their differentiation in the adult state, as well.
Collapse
Affiliation(s)
- G V Lopashov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | | | | |
Collapse
|
9
|
Navascués J, Moujahid A, Quesada A, Cuadros MA. Microglia in the avian retina: immunocytochemical demonstration in the adult quail. J Comp Neurol 1994; 350:171-86. [PMID: 7884036 DOI: 10.1002/cne.903500203] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Immunocytochemical techniques were used in conjunction with the QH1 antibody to study the morphological characteristics and distribution of microglia in the avascular retina of an avian species (the quail). The majority of microglial cells appeared in the outer and inner plexiform layers throughout the entire retina, whereas a few microglial cells in the nerve fiber layer were seen only in the central zone of the retina, near the optic nerve head. In the outer plexiform layer, microglial cells were star-shaped, with processes that ramified profusely in the horizontal plane. Fine process tips extended outward radially, insinuating themselves among the photoreceptors. A regular mosaic-like arrangement of microglial cells was evident in the outer plexiform layer, with no overlapping between adjacent cell territories. Microglial cells in the inner plexiform layer ramified through the entire width of this layer, showing radial and horizontal processes. Microglia in the inner plexiform layer also tended to be regularly distributed in a mosaic-like fashion, although there was slight overlapping between adjacent cell territories. Microglia density in this layer was approximately twice that in the outer plexiform layer. This pattern of microglial distribution was similar to that described in vascular retinae of several species of mammals, a finding that suggest that blood vessels are not responsible for the final locations of microglia in the adult retina, and that microglial precursors must migrate through long distances before they reach their precise destination.
Collapse
Affiliation(s)
- J Navascués
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Granada, Spain
| | | | | | | |
Collapse
|
10
|
Martín-Partido G, Cuadros MA, Martin C, Coltey P, Navascués J. Macrophage-like cells invading the suboptic necrotic centres of the avian embryo diencephalon originate from haemopoietic precursors. JOURNAL OF NEUROCYTOLOGY 1991; 20:962-8. [PMID: 1783944 DOI: 10.1007/bf01187914] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Macrophage-like cells have been previously shown within the suboptic necrotic centres of chick embryos during the period just previous to, and coinciding with, growth of the earliest optic axons through suboptic necrotic centres. In this paper, light and electron microscopy observations of chick embryos suggest that these macrophage-like cells originate from blood cells. Immunocytochemical techniques in chick-quail yolk sac chemeras, constituted of a chick embryo and a quail yolk sac, revealed that the macrophage-like cells within the suboptic necrotic centres are labelled with anti-MB1 antibody, which is specific for quail haemopoietic and endothelial cell lineage. These findings demonstrate that these phagocytic cells are of blood cell lineage, and originate in the extraembryonic tissues of the yolk sac. Diffuse staining around some suboptic necrotic centre macrophage-like cells suggests that they release MB1 antigens which may play a role in the growth of the optic axons through the suboptic necrotic centres.
Collapse
Affiliation(s)
- G Martín-Partido
- Departamento de Ciencias Morfológicas y Biología Celular y Animal, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | | | | | | | | |
Collapse
|